Well, a couple of shots from the hip:

1) Which version of XP Pro are you using (original, Service Pack 1, or SP2)? In the unlikely event you're not using SP1 or 2, you may be running into the "137GB limit" (aka "48-bit LBA not enabled" ) problem. See http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B303013 for details. Also, check your motherboard documentation for info on this issue; there might also be a BIOS setting related to this issue.

Since your system is "one month old", I'd be surprised if this is your problem (it also typically isn't an issue until you write more than 137GB of data on the drive, and the addressing gets screwed up and your system starts "randomly" overwriting existing data--you shouldn't see a problem with a freshly-formatted, essentially empty drive). This was a big deal three or four years ago, but is pretty transparent today.

2) Have you tried repartitioning and reinstalling the OS, just for kicks? Maybe your gut feel is right, and something did get corrupted during the initial install. Since you don't have anythng else on the drive, it shouldn't hurt to try wiping the drive and reinstalling. (Maybe you've already done this; your note didn't say.)

Good luck,
Jim

I can't believe how many people are having this type of problem. Well here was my situation.

Was backing up some data to a dvd when i got an error that locked my system up, so i rebooted. When I went to startup I would get the logo/load screen, it would go away after a normal amount of time and then the screen would just turn black. Tryed starting it up normally and got the mup.sys as my last loaded file. Tried a few things, the recover console chkdsk, the disable mup, nothing. I was reading posts on hear and one mentioned that they didn't have problems if they had a cd in a drive. Well, I have one dvd drive that sits on its own ide channel that is connected through a pci ide controller card. At the time it had a dvd sitting in it. I took the dvd out and volia, no more problems. Anyway, hope someone can find this helpful

Just experienced the same problem when building a new PC for a customer:

Asus A8N32-SLI Deluxe
AMD Athlon 4400+ x2 64
2 x Asus EN7800 GTX
4 x Kingmax RedTop 512MB DDR400 CL 2.5
2 x Seagate 300GB Ultra ATA 7,200
1 x Asus 52x QuieTrack CD-ROM
1 x Lite-On 16x DVD-R/RW DL
Lian-Li PC V1000 Plus Case
Windows xp SP2 OEM

I was trying to resolve some very slow boot time problems associated with the nForce4 chipset (see here http://forums.nvidia.com/lofiversion/index.php?t8171-0.html ) and changed the CD's and HD's to cable select this config booted once (still slow) and then got stuck on the mup.sys or whatever the next driver is on subsequent boot ups. I removed the secondary HD and the CD-ROM and everthing booted up without a problem and v. fast, so now I have the tedious task of working through the combinations of HD's, CD/DVD, cable select/master/slave settings trying to pinpoint the problem.

After having skimmed this thread it does not appear that mup.sys is the problem but any number of drivers or discoveries that come after, does any one know how to pinpoint the next process after mup.sys?

I'm having the same problem but haven't found anyone here posting the same circumstances. A couple times in recent days, when I clicked on shut down, the hard drive acted like it was busy and didn't shut down. So I shut it down from the power button. When I did this yesterday, it wouldn't start up again. Running in safe mode, I could see it would hang at mup.sys. I tried booting again and it ran chkdsk automatically, said it was dirty, and then cleaned it up and booted with no problems.

I got up this morning and couldn't bring it out of its sleep it had gone into overnight. Same problem, hanging at mup.sys. However, I have been able to get into safe mode if I wait long enough. It does move beyond mup.sys and launches in safe mode. I was even able to log in under normal mode once, but discovered it could no longer see the CD drive or an external drive hooked up by USB. So I shut down, trying to reboot, same mup.sys problem. So I went back into safe mode, and set it to run a full check disk, with /r /f on the next startup. It's running this chkdsk now, and has been doing so for about 3 hours, and is 68 percent through step 4.

I'm hoping it will work after this but does anyone have any ideas about this? I have a Dell inspiron 2200 laptop with XP Home and NTFS.

checkdisk found nothing wrong. A Dell compelete diagnostic test found nothing wrong either with any of the hardware. Still couldn't boot up so now have deleted original operating system and am installing XP Pro instead. .Will know in about 15 minutes whether this helps.

Paul: Your problem sounds similar to my case, which turned out to be the IDE cable. Later, I had a similar problem with a SATA cable. Before delving into master/slave jumper settings and drivers, try swapping the cable and see if that helps.

The Windows Pro XP install worked, and I was able to get into Windows again directly after the reinstallation and finish backing up everything to an external drive, but when I tried to shut down it hung up when the screen "Windows is shutting down" was present and I had to shut it off manually again. And it is back to hanging up on mup.sys again when I try to reboot. Does anyone have any idea what I should try next?

It will boot up, but it takes some time to do so 5-10 minutes. Also had one successful shutdown. On the first successful bootup it told me that mscvp71.dll could not be found. I'll just copy over that file from another computer.

In summary, what I seem to be having is incredibly slow start up, and perhaps incredibly slow or non-existant shut down. It's not an all or nothing thing like others have been having but is equally troubling. Any ideas about solving this once and for all would be appreciated.

N H: If you study this whole post, you'll find that your symptoms at bootup are actually identical to what some others have seen, including me (i.e., hangs after mup.sys loaded, but wait long enough and the boot will complete).

Another thing you'll find from studying this whole post is that unfortunately, there's a whole host of things that can cause these symptoms, and there's no guarantee that this post has covered all of them. Nothing in your posts gives me any clues as to where to start the troubleshooting.

If you were using a desktop, I'd point you back to some of the posts that suggest pulling out all the cards except for video and disconnecting all the drives except for the boot drive and see if that helps, then start adding things back in until you see the problem again. Since you've got a laptop, that approach probably won't work very well (I don't know nuthin' 'bout laptops).

Have you tried the list of suggestions at the top of page 7 of this post? Have you carefully read this post in its entirety, looking at all the posts that say, "I did this, and it worked for me" to look for other things to check, like relacing CMOS batteries, etc?

Good luck,
Jim

I actually have read all the posts in this thread-but a lot of the solutions simply weren't options for me-some due to it being a laptop and the fact that the components won't come apart as they are supposed to, others due to differences in the system-eg the bios settings available simply aren't the same as ones mentioned here. In any case, it is somewhat better now, starting up a little faster and always starting in normal mode, but installing XP Pro on a system previously running Home without a clean sweep of the drive has led to some instability and my CD drive continues to behave erratically-it thinks data cds are music cds sometimes and doesn't recognize the drive can write, and it refuses to install the proper driver. I talked to Dell this morning and they are going to send me the CD with the original software to make a clean install on the drive. If a clean sweep of the drive doesn't fix it I apparently am still under warranty until April and I will send it back for them to deal with fixing it.

Ok, my other system is crappin on me for some reason...It was running fine this morning, then I went into bios to change the AGP aperature from 64mb to 256mb and then the RAM timings from auto to 2-3-2-6, and thats it...I then saved and exited but window would not load. I get to the screen to choose what mode to start windows, and when I hit start windows normally or last known good config...it craps itself and restarts, and then when I choose any of the safe modes, it hangs at mup.sys and then restarts after a little while. So went back and load defaults into bios by hitting f5 and now it still does the same thing..What could I have done to make this happen?

ok, also, when i go to repair the install of windows using the disk, it says there is no hard drive attached and could find the OS...I check the cable, and bios recognizes the hard drive..what could it be?

Also when I put in the windows xp sp2 disk and tried to repair/reinstall xp, it said hdd could not be found...?

Specs of system with problems :
ASUS K8VB
AMD Athlon 64 3000+
Kingston HyperX 512Mb x 2
PNY GeForce 6800GT
80Gb Hitachi HDD S/ATA
Ultra X-Connect 500W PSU

I know its not anything hardware, cuz I plug in an IDE harddrive..formated it and installed windows...no probs..maybe hdd pooped itself? im goin to run diagnostics...

anyone got anything? thanks

I don't know, but you have not indicated that you are seeing the same failure signature (bootup hangs after "mup.sys" when starting in safe mode) that this thread specifically addresses. Perhaps you would get better response starting a new thread.

did you not read what I said fully, here...I'll quote myself
"it craps itself and restarts, and then when I choose any of the safe modes, it hangs at MUP.SYS and then restarts after a little while." -Me (from original post)

so what didn't I specify?

Whoops--sorry, I did miss that. Still, it's clear that your bigger problem is not, "my computer won't boot", but rather, "my computer (or at least Windows) won't recognize one of my hard drives". I thought you might get a better response to that problem if you started another thread. I bet most folks on this forum stopped paying attention to this thread a long time ago.

Two things I'd ask you to clarify:

A) What is the distinction between the Windows Installer not finding the hard drive and/or previously-installed OS when you attempted the repair install, and "Also when I put into windows disk, said hdd could not be found...?" (I don't understand what you mean by "put in the Windows disk" or why it would be looking for a hdd, unless you're talking about trying to do a repair install, which you already mentioned...)

B) "...cuz I plug in an IDE harddrive..formated it and installed windows...no probs." This implies that the hdd you're having trouble with is non-IDE, but you don't indicate what interface it does use.

I have seen the Windows install disc act "oddly" (not finding hard drives, not finding previous Windows instances and offering the repair install option) in two cases: (1) When multiple hard drives are installed, and (2) when hard drives are connected via an interface other than the primary IDE interface.

For (1), I've always been able to get the repair option if I removed all physical drives except for the boot drive.

For (2), the Windows install disc gives you the option to load drivers for other interfaces (SCSI, RAID, etc.). In my case, I have both the old parallel ATA and the newer serial ATA interfaces built-in to my mobo. Windows works fine with my PATA drives, but it sometimes acts flaky with some PATA drives I have that use a SATA adapter (the drives work fine in normal operation; it's only Windows Installer that has a problem with them). I've (fortunately) always been able to rearrange which physical drives are connected to which PATA or SATA connectors to get around this problem before.

I don't know if either of those might apply to you.

Jim

Well, I fixed the things you were confused about...
"Also when I put in the windows xp sp2 disk and tried to repair/reinstall xp, it said hdd could not be found...?

Specs of system with problems :
ASUS K8VB
AMD Athlon 64 3000+
Kingston HyperX 512Mb x 2
PNY GeForce 6800GT
80Gb Hitachi HDD S/ATA
Ultra X-Connect 500W PSU

I know its not anything hardware, cuz I plug in an IDE harddrive..formated it and installed windows...no probs..maybe hdd pooped itself? im goin to run diagnostics..."

Well, I ran some diagnostics tests on the hard drive, and it passed.. well, it passed one, the other program couldn't find the HDD...I only have the one HDD installed in this computer...I just can't get past mup.sys so that I can get into windows and copy files so that I can format the beast...lol

Sounds like what I experienced working on a co-worker's old Dell recently. It would POST very slowly, and no matter which mode I tried booting in it would get just past mup.sys then flash a blue screen real quick and reboot. I ended up having my digital camera ready and got a snapshot of the blue screen which had an error about a registry file not loading. The Dell mobo didn't have a clear CMOS jumper so I just took the battery out for a few hours. After I put the battery back in it would show the HD in BIOS but during POST would say it couldn't find the HD or OS, and it was still very slow and flashing the blue screen and rebooting. I decided to format and reload the OS, but it took 3 hours just to load the setup files from CD (usually takes less than 30 min). The guy said somebody had done some work on either before or just after he got it, so I looked at everything and discovered the memory had been upgraded to a 256mb PC133, while the mobo only recognized 66 or 100 due to the Intel 810 chipset. I had a couple of sticks of PC100 so I swapped the PC133 for 2 sticks of PC100 and Viola! the machine booted normally and I was able to get Windows loaded normally. Oh I forgot to mention, the machine is a P3 533 which originally had NT Workstation but had been upgraded to XP Home. I reloaded it with XP Pro Sp 2, did all critical updates, installed Avast, SpyBot, Adobe reader and a few other utils and everything is fine.
Jim, I was thinking that since different PCs load different files right after mup.sys, perhaps a good piece of advice to give to everybody would be to go into safe mode while the machine is working fine and make a list of the file(s) that load after mup.sys so they would at least have a starting point for troubleshooting. A couple of folks who have posted here have mentioned agp440.sys, but on my main machine XP Pro loads giveo.sys then agp44.sys right after mup.sys. Remember folks, it isn't mup.sys that is actually the problem, it's the file that is supposed to load immediately AFTER mup.sys. Knowing what that file is might give you a better direction to start figuring out what went wrong. My original post on this problem was on a Win2K SP4 machine I had simply switched memory in. After I corrected a problem in Device Manager everything was and still is fine.

I forgot to add another piece of advice: if you only have 1 actual hard drive, ALWAYS have it partitioned into at least 2 virtual drives. Make your c: partition 10-15gigs for Windows ONLY and keep all your important files/docs/pics etc on another partition (normally d This way if Windows goes bonkers and you're faced with a format/reload, you don't have to spend alot of time trying to recover stuff. I have 2 drives with at least 5 partitions including a "swap" partition on the 2nd drive for the pagefile.

I encountered this today at a clients house, Windows XP Pro that I headed to based on "network cable unplugged" messages she had been getting. when I got there it was Blue Screeening when trying last known good config and normal mode saya IRQ NOT LESS THAN TOTAL essentially either IRQ conflict or Buffer overflow due to bad software or registry issue
she had an older PC
Pentium 3 750MHz with 256MB PC133 ram

tried to usual removed old 56k modem and NIC no change tried safe mode and would freeze up on system32/drivers/mup.sys

as per the BSOD message it suggested to try disabling video caching and BIOS caching in the BIOS

entered the BIOS setup and found them both under "advanced Chipset setup" once disabled, windows booted fine althogh she had other miscellaneous errors they were easy to fix.

funny Google search brought me here and first post is nearly 2 years old and is now 20 pages long hope everyone tries this as it worked for me and finally a BSOD message that suggested something that worked.

Cheers
Michael P.
Kelowna, B.C.
Canada

I just got a new motherboard, a MSI-915 and a new Connect3D X800GTO. The hard drive is a 200 gig PATA hard drive from Maxtor. Once everything got connect i booted up my computer as normal and Blue screened. I Rebooted and ran it in safemode to see here the problem was an it, like everyone else was in the mup.sys. I run off windows XP and i'm desperate to get my computer up and running. my motherboard uses the Phoenix - Awardbios CMOS setup utility if that helps. If you could please either repost or email me at ptimus_Pryme@hotmail.com">Optimus_Pryme@hotmail.com if you have an ansewr that would be amazing. I finally got up to a good video card and i haven't been able to use it since i bought it. Thanks in advance