Might be good to use a utility like smartctl and activate the onboard SMART diagnostics of the drive.

EDIT: Perhaps give this a try, it has smartmontools on it:

http://ubcd.sourceforge.net/

Try yelling at it a lot.

So what exactly should I do to properly diagnose the issue? I don't want to end up losing all my data. Temps are fine, as I've been running Motherboard Monitor for a while and haven't seen any changes. I was thinking HD, but how do I check it? Also, isn't there a "memtest" function that can test my RAM? Let me know what the best course of action might be. Thanks for all the help so far!

Not sure what part of that boot CD stuff I need to use... sorry, I'm a few notches down in skill from your average PC builder. I have a fair amount of knowledge, but not a ton. A few more specifics would be great! Thanks.

No problem. I have never used this CD before myself, but I will download it and burn one so that I can walk you through it. This CD should allow you to run hard drive diagnostics, among other things

On the UBCD page, there are several mirrors where you can download a file. Here is a direct link to a script that you allow you to download the .EXE file.

http://www.fulminati.org/ubcd-exe.php

We'll take it to that point. From there I think we can double click the executable to create a bootable CD. Mine will be downloaded in about 12 minutes, you can either wait and I'll post back how it went or you can start downloading the file, either way.

Alright, I just enabled SMART in my BIOS, but I guess I need some kind of software to interface with the drive and see about its status?

And, by the way, if you haven't backed up any data, it might not hurt to do that at this point. The actions that are performed by the CD will be non-destructive from a software standpoint, but if your hardware is failing, it might be good to "get what you can when you can"

Correct. Also if your BIOS is not set to boot from CD, you might go ahead and make that change at this time.

Thanks for the help, BvSSE. I won't be able to work on this much more tonight, but if you're in the middle of downloading and want to post some tips, I wouldn't complain :P. I'll hit it later tonight when I get home or tomorrow morning. I appreciate the suggestions a lot. I'll definitely set up the BIOS to boot from CD right now before anything bad happens.

Also, are you suggesting that I go ahead and snag another hard drive to copy some data? I don't want to spend unnecessary money, but if we're pretty sure it'* the hard drive I don't want to lose data, either.