At a friend's suggestion, I tried having Task Manager open to check if a particular process was suddenly using a ton of CPU during the freezes, but Task Manager froze as well, so I couldn't see anything happening. I tried rebooting the computer several times, which had no effect. I ran a virus scan using AVG Free, and another scan with Spybot Search & Destroy. They both found several problems (I haven't run scans in a while), which were then resolved. Rebooted the computer again, but the freezing still occurs. After poking around on Google a bit, I tried running CHKDSK on my C drive, since I turned my computer off improperly right before this started occuring. No problems. I also tried running a scan with Malwarebytes' Anti-Malware, which, like the other scans, found several problems and deleted them. But, the freezing still happens.
I really don't know very much about this sort of thing, so I have no idea what else to try now. A friend directed me to this forum, so here I am. If anyone has any ideas of what the problem is, or how to figure out what the problem is, it would be greatly appreciated.
(My apologies if this is in the wrong section, but I really have no idea what the issue is, and I am using Windows XP, so.)