Turning off "Automatically restart" option has no effect, computer will reboot or hang with no video signal (black screen) where computer is under high load (processor / disk / network). Could be red herring, but have found that if I keep the Handles figure reported in Task Manager below around 10,000 can keep computer running. Until recently I could get my computer to crash on demand by loading a file into "Adobe Photoshop Elements 2" if I already had a few programs loaded. I then switched my NTL broadband connection from USB to Ethernet as I found the crash did not occur in Safe Mode with Networking disabled. This has reduced the number of crashes and loading Photoshop now rarely crashes the computer. I could live without Photoshop, but the crash occurs other times as well. I have used a memory check program (Microsoft's and other) to test the the 256 MB RAM and have installed the latest NVidia video device drivers.

Voltage problems perhaps with the CPU, is it overclocked or anything..could be having adverse effects on the RAM if it is

Thanks for your reply. I know virtually nothing about the hardware aspects of PC's but I would hope the possible causes you mentioned are unlikely as I didn't build the PC myself, but bought it from Carrera SSC, a well established PC manufacturer - but I wouldn't rule it out either. I hope they have used reasonable components, which include the Asus A7N266-VM motherboard etc. The fact that it never crashes unless applications use in total more than 10,000 handles hopefully gives a clue. For example, at present it is running quite happily with a multi-threaded program that I have written that uses IE automation to control 15+ instances of IE to gather info from specific Web sites. With this running processor / network are earning their money's worth and HD is not idle either. Handles presently 9300 and virtual memory 320/1024MB. So, this would suggest to me that the hardware is essentially ok because the processor / memory / hd / network will be pretty much fully utilised with my app running. But if I now ran Photoshop, which is rather resource hungry, it could well crash the PC. I suspect Photoshop is not the cause of the problem, it is just highlighting the cause as the computer has crashed on lots of occassions if too many instances of IE are loaded, thus using lots of resources.

Sounds to me like it's a memory problem. I don't know what memory tester you used but try this one. http://www.memtest86.com it's a very good program and if there is a memory problem this should tell you.

Memtest-86 was the other memory tester I used. I have just re-run this in standard and extended modes for an hour each and no errors were reported. I have also tried Asus PC Probe to check processor/motherboard temperature and voltages - declared OK.

Go here and try this out http://www.utilitygeek.com/details.php?fileid=154 this might help you narrow it down to whether it's a hardware or software problem. It's not one that I've used as at my work we've purchased a similar program but this one is free. If it doesn't come up with any problems I would start using msconfig and turning off startup programs and see if that gets rid of the issue.

Thanks "freekt" for your suggestions. No hardware errors were reported by "Hot CPU Tester 4", so based on this and the other tests I believe that it was most likely an OS software issue. I actually haven't had a crash since Wednesday, after loading the latest two critical security updates for XP and IE - so it's just possible Microsoft have fixed what ever was causing my crashes. Having said that, this morning my computer (a desktop) inadvertently went into hibernation mode... I'm going to stick another 256MB of RAM in it to see if that keeps it happy!