PC keeps freezing

During the summer it would be pretty hot so the pc would feeze. I would a large fan near the cpu that would fix that. Now in winter has happened serveral times I would just browsing youtube or the net PC will freeze. Win 7 X64 Athalon X2 core 4 Ggbs DDR2 ram. I know its an old computer but what the hell is wrong with this crap
Answer #1
Try cleaning the dust out the fan. Could be as simple as that
Answer #2
If heat is the issue, this will solve it. It also might be an HDD going bad. You can check you temps with HWMonitor:
http://www.cpuid.com/softwares/hwmonitor.html
If its not temps, I would check out the HDD(s). For this you can use HD Tune Pro. This link should be working still:
http://www.google.com?t=13539149