my computer just restarts when it feels like it.
i have updated the bios, but mine was already the newest one, upgraded the PSU from 300W to a 400W, that had no effect. onboard sound is disabled

Jetway KT400 series v400ADB
AMD AthalonXP 2000+ (133mhz)
soundblaster live player 5.1
nvidia gforce4 mx 420
2 60gb hds
2x256mb ddr ram
belkin wireless network card

HEAT, take of the side of the case and blow a fan onto the internal components. Also, recheck the connection from your heatsink to your CPU. CPU overheating will cause lock ups and or reboots. Depends on how your machine is set up.

i dont think its a heat problem, heatsink is on ok, and it is well ventilated. also the option for the computer to restart if it overheats has been disabled

Well first off,If you dont know what the operating temp is of your machine then you dont know about the heat issue. Assuming is dangerous. If your machine is running within specs then its not heat.
The other thing i would check , if you are running 2k or XP then check System Properties, Advanced,Startup and Recovery and make sure the System Failure box has Automatically Reboot unchecked. If your getting BSOD's and its checked then the problem is hidden from you because of the restart. Usually though. IT will flash a error before the reboot.
The other thing it could be, is a short or a piece of hardware going bad. Random errors, assuming all the above is not the issue!, are almost always hardware related. Try taking out one RAM stick. Check all connections.

the system is running fine,, just the restarting bit. i checked the auto restart, and it was ticked. cho i unchecked it. the system logs (in the system log) the following error after it restarts "The computer has rebooted from a bugcheck. The bugcheck was: 0x1000008e (0xc0000005, 0x805322c1, 0xf5267644, 0x00000000). A dump was saved in: C:\WINDOWS\Minidump\Mini120503-06.dmp."

Hello. I have an AMD Athlon K7S5A (?), 1.4 GHz pc with Windows XP. I have the same problem that you do. My computer restarts randomly. I always thought it was because of the fans and because I seldom turn my computer off. However, last night it just shut down and wouldn't turn back on again. I tried the key on the back and it still didn't work. I tried it again this morning and finally managed to get it to turn back on but after about 5 minutes it shut off once again. I have no idea what's wrong, and was hoping someone out there could help me.
Thanks.

Runnign fine except for reboots ;p
lol. Are you overclocking anything?
Also, I would goto windows update and update then I would look for new motherboard drivers. Make sure the drivers you are using are on the whcl. Then I would run chkdsk /r /f /x
disk corruptions can also cause em.

I haven't overclocked anything. I haven't changed any system specs since I got it. I will look into new motherboard drivers but I hope it's not expensive. You mention whcl what is that? and how can I run chkdsk /r /f /x ?
Thanks for your help.

Motherboard drivers come from the manufacturers web site and they are free.
WHCL = Windows Hardware Control List. Its basically a list of all the hardware MS says will work and they have tested drivers for.
Easiest way to run chkdsk -->start, run, type cmd, type chkdsk /?
This is a list of what parameters you can run with CHKDSK. I would be sure and run it /F /R /X The dismounting means that it shoudl run then and there without reboot, But using jsut /F and /R willr equire a reboot. Either way, it is a very useful tool that many people don't use. Its especially helpful when you have a shutdown or power off and someone how your boot process is hosed.

The best thing to do guys if you are running xp or 2k is go into the control pannel open administrative tools, you may have to do this in safe mode(keep pressing F8 at power on enter safe mode). Once in administrative tools click on event viewer, on the left hand side of the box that opens up are application and system, if you click on one of these it will open up a list on the right. Scroll down this list on both application and system and look at any of the comments in red which say error. Double click on the error and a box will appear, you can now either press on the link and go to microsoft to find what the fault code means, or try and find the most common ones and post them back on here.

Alternatively to this it could be faulty ram casuing this problem, try downloading a program call goldmem (gold memory) its a ram testing software, it will only work on 1 stick at a time. You can run it off a floppy disk from dos.

Post back results please.

Laters

you had any luck yet ?