I only have one stick of RAM in there.

Asked me IT teacher today and he said:
Run a scan disc with both options checked set for when your PC is restarted. Then run a defragment, if you crash while in defragment mode, the you've been "fraged" so you need to backup your data ASAP and then go and buy a new hard drive.
He also said something about a program called something like Memcheck.

I'm about to run the scan disc so I'll say how it goes soon.