Computer Randomly Locking Up While AFK - Win7

[Jotaru]

So I'm completely baffled. I'm running Win7 and for the past.. few months? its been locking up on me. It never happens when I'm using it- it'll only occur when I go afk. Sometimes I'll be gone ten minutes and its locked up- sometimes i'll come back hours later and its fine. It doesnt happen too often, but its often enough to be annoying, as I have to hard restart whenever it does (2-3 times a week)

When I get back to my computer, the mouse will work (cursor moves on screen) but absolutely nothing else is responsive. Keys do nothing, clicking on things doesn't do anything, if I have anything open I can't click to get a blinky cursor to type.. nothing. Also, when I try to use it, I hear a fan speeding up inside- not sure which fan, but it happens every time. Usually I restart before too long because I'm afraid its going to overheat or something. A few times I've just waited (up to 10 mins before) and it does not un-freeze.

I didn't install any new software/hardware that I can recall when it started happening, and I can think of no way to try and figure out what exactly is going on. I've used Spybot, I've used antivirus, picked up nothing.. I'm at a loss. Any tips / advice?

[Cephius]

I'd check your power settings to make sure the computer isn't set to try to hibernate or standby after a certain amount of time. Also, check your major hardware - video card, nic card, etc - and make sure the "allow the computer to turn off this device to save power" option is unchecked. My guess is something is turning off and not getting turned on properly.

[xopher]

what do the event logs say

[chiyio]

that sounds like the hard drive has spun down and isn't spinning back up like it's supposed to. Make sure it's set to never spin down in the power settings.

[Jotaru]

I know how to pull up Event Viewer but no clue how to find what I'd need.