I am experiencing a problem, the cause of which is proving to be very tricky to locate. Perhaps someone out there will have experience of a similar thing or maybe some other ideas to put forward.

I have 'upgraded' three machines, two in an identical manner with the third being similar. In fact the upgrade represented a complete rebuild, retaining only the case, PSU and floppy drive. The new spec of the two is as follows...

Disk Hitachi 40Gb
Mainboard Asus A7N8X
Processor AMD Athlon XP 2500+
Graphics sparkle 32MB AGP
Memory 256Mb PC2700 DDR
OS Windows XP Pro

(the third machine is similar but with 512Mb RAM, a CR-RW and 750Mb ZIP drive and a lot of application software - but shows no problems)

Machine 'A' has been running without problem however machine 'B' has shown the trouble.

Before moving to the new system running XP, the machines were running an old DOS application for 3-4 weeks and no problems occurred however having now started using XP (which *could* just be a coincidence) very occasionally machine 'B' will either lose its signal to the monitor and refuse to start up again or will simply reboot itself. In the first case the main unit has power on although I've not been able (yet) to find out whether it is still running (via the network) and the only way to get things going again is to switch off the machine.

This problem is so occasional that the machine can run for a week or more without problem and then it can suddenly happen (when starting up from cold).

At the moment I'm trying to eliminate (or detect) faulty hardware by swapping over components and have ruled out the graphics card. I've run extensive memory tests on the RAM with no problems found and have currently swapped the memory and CPU and am waiting for a failure to appear somewhere.

Could it be a software problem?

I do recall that when I was putting the machines together I had problems installing the supplied drivers for the graphics card and it would only work on one of the machines, the other two machines would crash and so were built using the default XP drivers. Sadly the notes I made at the time detailing whihc machine was which in this case have gone missing.

One job I obviously need to pursue is to try and get some better graphics drivers and see if they help.

Any other ideas?