Firstly this question leads on from
As the problem reappeared again merely hours later.
In trying to solve the problem I've tried a bunch of things and I'm pretty confident the issue is related to CPU temperature, that is when the temp is high (50-60 degrees) on a P4 3.0Ghz, things tend to fail, on the other hand when it's low (40-48) it seems less likely to fail.
This is a multipart problem - firstly I'm fairly confident that the temperature is related to the problem from much trial and error, but I haven't been able to find info about what temperatures are acceptable for a P4. So what are they?
Secondly, while trying to keep the machine cool, I've used Speedfan to adjust the fanspeed in an upwards direction (from 33% to 100% - very noisy but it works better) - however the fanspeed drops to normal a second or so after going up, even though speedfan claims 100% neither the noise nor the RPM match this. I've had to tap speed up and slow down quickly in order to keep the fan steady at 100% speed. Why is it doing this, and how do I fix it?
Thirdly, I've been looking in the BIOS for some options that might help, things I'd been hoping for include underclocking the CPU to gain a bit more stability, putting the default fan speed up, and searching in vain for a 'break randomly = Enabled' option I seem to have had on since recieving the PC. The bios seems to lack any of these features. As such I'm looking to update it - I can't find an updated version of the BIOS on the system manufacturers site, in fact the site drives me insane with circular links and misdirection, moreover I don't know for sure which of the many brands of Acer Aspire I've got.
PC info: p4 3.0ghz, MB model# E61ML, BIOS ver#R02-A4, 1GB RAM, Win2k.