You can get a thorough system test suite in UBCD (Ultimate Bood CD). The self-booting CD tests multiple system components: memory, CPU, hard drives, peripherals, etc. It does a very thorough job and is extremely easy to use.
Although it's reported version ver4.1.2 is available, the latest version I could obtain was 4.1.1 http://ubcd.sourceforge.net/ http://ubcd.sourceforge.net/download.html
You can download a .iso, .exe self-extracting, or .zip file depending on what connection speed you have. (download filesizes range from 87mb to 115mb) The .iso file is easiest as you just download it and then burn the .iso image to a CD using Nero, or CDburnerXP, or burnatonce, etc.
I just went through this with an almost EOL machine.
I'm not sure what caused my problem but I narrowed it down to being my IDE devices suddenly causing a problem with Windows. Could have been an update for the OS or the way the OS handles the BIOS. I diagnosed this by pulling all the IDE devices but the OS HDD and the machine booted without problem. So I at least knew where to start looking.
Previously I ran everything configured to CS (Cable Select). My fix was to set each physical device with their jumper as either MA (Master) or SL (Slave). After doing that I still had problems until I connected the MA set device to the connector at the end of the IDE cable and the SL set device to the connector in the middle. I didn't realize before that that it mattered which device went where on the IDE cable but I guess it does.
Anyway all things fixed and no problems since then even after multiple reboots and days of uptime.
I guess this could be OS related as I mentioned or maybe my IDE controller has issues or one maybe more of the devices was not signaling correctly when set to CS mode.
Putting the master drive on the end of the cable is done for electrical engineering reasons in cases when you don't have a second drive connected to the same cable. It has to do with signal quality of the data and control I/O lines. You always want at least one drive at the end of the cable when the IDE port is used. If interested, it comes under the category of transmission line effects.
And yes, the master/slave select can depend on cable position as well. Contrary to what some people say, it can pay to read the instructions.