My Windows 7 almost always restarts when I keep it idle for ~20-30mins. It happened randomly before, but lately, if I leave the computer I can be sure it's gonna restart after those 30mins. It never happens when I play games or work tho, just when it's idle.

It's a fresh install of Windows 7 64bit. I had also problems while installing it, it always crashed while finalizing the install and I had to reinstall again. Eventually it installed on 3rd or 4th try after I deleted all of my partitions and added them again.

I thought it might have been a hardware problem, but temperatures seem to be okay and I have no idea how to track what might have been causing it.

Any ideas?

I'm running Windows 7 64bit on:

• Gigabyte EX58-UD4P
• Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz
• NVIDIA GeForce GTX 260
• 6GB of DDR3 1066Mhz RAM
• WDC WD1001FALS-00J7B0 1TB SATA II

I have a very bad feeling it might be something with HDD and its compatibility with Windows 7 as I haven't had those problems for 1 year while I had Vista.

Edit:

I checked Event Viewer critical errors from this night. PC restarted first time at 11:12pm, then at 3:06am and since then every ~20min until I came back to it.

Error message is:

The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.

Source: Kernel-Power