Thanks for your reply.

I only downloaded mp3 files - no exe's or anything. Perhaps somewhat stupidly, I didn't have any anti-virus software installed. Maybe this is a silly question, but can mp3 files give you a virus? Or the spyware that may have been put on my computer?

Perhaps it's just a coincidence that the problems started happening when I was using Limewire (it was the first to crash). At this point I just need to figure out how to fix it, whatever the problem is!

Any ideas?