A friend's computer had been suddenly rebooting after being on for a half hour or so. It would happen to him every day. I thought his power supply might be sagging so I took my supply and put it in his machine and put his suspect supply in my machine. He has been running fine every day for about a month now but e-mailed me today that he had another sudden reboot (the only one in about a month). His machine had only been on for a minute or two before this reboot occured so I don't think heat has anything to do with it. His old suspect supply has been running my machine just fine. I'm going over there on the week-end to give his machine a good cleaning, fan lubing etc. but I can't think of what could be causing this (very intermittent now) rebooting. If anyone has a suggestion of something I could try I would appreciate it.
I had this problem on a cheap Celeron PC. I reformatted the hard drive and the problem persist. Then I swap the CPU then it stopped. By this time the CPU was outdated so I junk the PC.
I had a similar problem running Win2K. The problem manifested itself most when machine was heavy load. I changed PS with no improvement. I finally added more RAM and the problem went away. I suspect a "feature" in Win2K where system, essentially, gave up when it ran out of some resource.
You might give the RAM increase option if you're not already running with a BUNCH.
An aside - it really hacks me that an OS would fail so "ungracefully/disgracefully". I never have had that with UNIX or Linux
- sure wish I could get all features of MS apps on one of those, then bye-bye MS.
I had a similar problem with an HP Pavilion computer here (running Win ME). Celeron 700 Mhz. This is the machine that the kids use on the internet, and as such is subject to daily bombardment from a myriad of sources. It has current virus ware and firewall, spyware blockers, etc., but still things happen. After the machine had been in use for two years or so, I began to notice an extremely high level of hard drive and CPU activity (nearly constant), and it would occasionally do a reboot as the OP described, completely on it's own. For whatever reason (no doubt Win ME was a contributing factor), this machine had things running in the background that were no longer under user control. The excess HD and CPU activity taxed the minimally capable power supply in this machine to the point that it would reboot at will.
In my case, I upgraded the RAM, installed a new Phoenix BIOS, formatted the drive, and installed Win XP Pro. Might be overkill, but the machine works much faster and smoother now. The XP Pro also gives me the option of setting up accounts for different users with different security levels, which is more appropriate for the way this machine is used. Swapping the BIOS has the added advantage of removing some of the handicaps that HP built into the machine too.
So, the question is, does your friend also notice a lot of hard drive/CPU activity on his machine? How long has it been in service? On what operating system? Is it internet connected? Is it just possible that a clean sweep of the HD might be in order? I am am only suggesting this (from my own experience) as one possibility. It would also be one possible explanation why the swapped power supply had the described results. The supply he swapped into the machine may be more capable than the original, which would explain the lower occurrance of reboots, though the problem continues. It may well be a hardware problem too, and this may not apply. Your mileage may vary, etc. Good luck.
Thanks for the ideas everyone. I think I'll start with some BIOS (DDR) adjustments then a good virus scan of his system after I've cleaned the machine, lub'ed the fans and re-seated all the cards.
1 - Memtest : you can get memtest by burning a mini distro of linux. like Knoppix. Knoppix is also a handy toolkit in case you need to recover data before reformatting stuff. So google it up ;) Reseat/Clean/Replace memory module if necessary.
Check CPU temperature : somebody has suggested this already. Rising CPU temperatures may cause reboots since the ACPI side of the bios will halt the whole system once a specific temperature is reached.
Try using HijackThis : Using that would let you check any programs that may load during startup. It could be a trojan/malware/worm that is causing his PC to reboot. Use reliable antivirus and dont forget to update.
Do benchmarks : doing benchmarks would give you a big eye view of how the computer performs and make considerations/recommendations on how to fix it.
Check for any kind of invalid/broken tweak for video. Sometimes tweaking the VGA card too high may cause failures. Reinstalling the Video card would make the settings go back to its default state.
Investigate on what program hangs and if necessary, download appropriate patches for it. Patch your windows as well.
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