Hey guys, this is the first time I've been here and I hope I can find someone who has some advice because I've never run into an issue like this before.

For the past week my computer has been crashing for no noticeable reason. It will crash but not reboot. Turning the computer on again will start everything but the CPU cooling fan and video card. To the best of my knowledge there isn't a temperature issue as I installed a new CPU fan and heatsink 2 months ago and have had no issue til now.

The only way I've been able to remedy the situation is to completely remove the heatsink (unplug it from the motherboard and remove it from the cpu) and then reinstall it. Doing this will allow my computer to boot up again and run normally.

Things I've tried:
Clean windows registry
Windows repair
Clean off and reapply new thermal grease to cpu
Run anti-virus, malware and spyware checks

I'm not positive if this is a motherboard issue, but having to disconnect and reconnect from the motherboard has led me to believe it may be a factor.

Average temps. I'm running is mid 20'sC for the core and high 30'sC for the board.

Here are my comp specs:

Windows XP Pro x64
AMD Athlon X2 4000+
Ultra 750w Power Supply
2048MB DDR2-800 RAM
ECS GeForce6100SM-M2 v 1.0 motherboard
256 MB GeForce 8600 GT vid card
WDC 80G hard drive
Katana II CPU Cooler

If anyone needs more info just ask and thanks for your help.

First, by "crash" do you mean your system just locks-up, or is there an error msg? Suggest in the future you separate the 2 in your posts, system lock-up vs crashes.

By "everything but the CPU cooling fan and video card" do you mean that your system will not start anymore from a cold boot? (full power-off, then power-on)

The CPU fan NOT starting is a very big issue. This may be the cause of your problem; especially if you motherboard has "health" monitoring capabilities, your motherboard may be shutting off because of limits reached.

If you CAN boot your system, suggest you try HWMonitor (freeware, see screenshot on page), and at the desktop run it in the background and monitor temps, fan speeds, and check occasionally for fan speeds in this case. Note this utility works IF your motherboard uses Industry Standard Temp/Speed APIs. Also, sometimes the CPU Fan speed may not show, try exiting the utility and reopening. The download IS the application, not an installer, you place it in a folder of your choice and create a shortcut to it. I have one shortcut in Accessories and a copy in my Quick Launch Bar.

Another issue, check all your Power Options, in Control Panel. EVERYTHING, except the Monitor, should be set to Never, and Hibernate should be disabled (unchecked). Unfortunately WinXP tends to default to laptop settings.

First of all, thank you for your response.

By crash I mean the computer just turns itself off, no shut down sequence or anything, just immediate shut down. However, sometimes it doesn't completely turn off. I'll look at my case and my case fans and power supply will be running, but my cpu fan and vid card fan won't be.

"By "everything but the CPU cooling fan and video card" do you mean that your system will not start anymore from a cold boot? (full power-off, then power-on)"

That's correct, in both situations, when the computer turns off (unexpectedly) and it's completely off, or its off but the case fans and power supply fans are going, the system won't turn back on unless I remove the heatsink from the CPU, disconnect it from the motherboard ... then put it all back on.

I will try that freeware today and let you know how it goes. Also, is there some software I can use to check my power supply? I'm not sure how to tell if it's failing or not providing adequate power or something. It's a 750w supply so, assuming it's operating normally, it shouldn't have any problems running my machine.

As for the Power Options I have all that setup already, and confirmed that those settings are still there so that's taken care of.

Thanks again for the response. Hopefully I can diagnose this issue soon.

After looking over HWMonitor I noticed something a little disturbing with my voltages. My readout was:

+3.3V: 1.86V
+5V: 5.67V
+12V: 4.80V
-12V: -11.04V
-5V: 0.27V
+5V: 5.16V

I don't know a lot about voltages ... but arn't those values only supposed to be +/-10% of their respective base values? Seems like this may simply be a case of needing a new power supply?