I've run an extensive scan with MalwareBytes, Spybot and Trojan remover. I use Avast for general protection. I ran CCleaner. The partion where Windows has been installed has about 2gb free of 50gb (I'll free some more, though it never really helped before).

Open task manager and go to the performance tab and see what is going on when it happens.

''The partion where Windows has been installed has about 2gb free of 50gb''

That can't be good. Personally I wouldn't feel comfortable having less than 10GB free space on the OS partition. Why don't you extend the partition in Disk Management.

I figured somebody would say that. I freed up some space on it anyway. As for partition extending, I didn't know you could do that without deleting the partition . I'll try it now. One thing that is notable though, is that on one of my hdds, videos sort of snow (static, like a TV with no signal) and are disfigured or distorted. Its also not playable. Copying the video file to another hard drive makes the video playable but some of the distortions are still there. Videos on other hard drives (from LQ up to HD vids) play just fine. I think my PSU is also just about had it as well.

I had gone through same, it was due to bad sectors on hdd. If freeing up space didn't solve ur problems. Run scan for bad sectors on the hard drive you suspect.

Yeah Acid, this is was my last resort, reinstalling windows all over again on a different drive... So much fun. I've backed up the important files from the failing drive now so, lets see what happens.

After a fresh install of windows on a new drive, the slow down seems to have totally disappeared. So it was a bad drive indeed, or so it seems. I suppose time will tell if the issue resurfaces... Will still look into getting a new pc though. Thanks a span for the assistance folks.