High end(?) computer suddenly suffering long load times and random stutter
So I have a Cyberpower computer that's only about 6 months old. I think it's overclocked, I game a lot, and sometimes I leave it on overnight, maybe even 2 nights in a row even though I was advised not to (not sure if that's relevant). Here are the specs:
Windows 7 Home Premium
Intel Core i7 (8 CPUs) 3.7 GHz
16 GB RAM
AMD Radeon 6800 Series
1000GB HDD with 641 GB free complemented by a 100GB (I think) SSD
Up until yesterday, I have never upgraded any of the drivers, the Windows 7 software, etc. I shut off Windows Update because it hogged all my bandwidth and usually updating Windows broke something until it updated again.
All of the sudden, yesterday, I started having issues with TERA taking forever (read: About 5-6 minutes to get all the way in-game) to load when it had been fine before, and once in-game, NPCs failed to load correctly at first. I later tried to load up Far Cry and it took literally almost 2 minutes to load just the level. I then, just to test, tried loading up The Witcher and Hard Reset. Hard Reset took about 3 minutes, the Witcher took somewhere in between 3 and 5. All of them had noticeable stutter. It wasn't often (30 seconds-ish in-between), but it's something that has never happened before. Then, later, the load times went down significantly while still seeming a lot higher than usual. The stutter when I shot went away in Hard Reset. Didn't check all of them.
Yesterday, I updated the AMD Catalyst drivers for my graphics card. The first download ended up being corrupted during install, so I re-downloaded. The install worked, but the driver was still reading 11.9 (the current one is 12.4), and it still said there was an upgrade available. So I redownloaded the installer and installed it again. Nothing changed.
Today, I loaded up Psychonauts, and while it loads pretty quickly, some areas are stuttering like 1 stutter per second. It's pretty noticeable and probably shouldn't happen.
I still haven't upgraded Windows itself.
I don't have an antivirus, but all the sites I've been to since the issue started and before I noticed the issue. The only ones that I wasn't 100% sure about were the HPSSims site (creators of Tigers Unleashed, been featured here, Google Safe Browsing said 55 pages or so were clean), and the open source Ur-Quan Masters site and download, but it's pretty popular so I gather it's safe (EDIT: Oh, and the Spy Party site, which I'd never been on but I gather that's safe too :P). All the other sites have been regular forums, blogs, etc I visited long before the issue.
I really don't know what could be causing it, barring that my computer is slowly wearing down after only 6 months.
Thanks in advance.