[black hawk]

Nowadays, my computer usually hangs after every 20 minutes or so. At first i thought that it was due to some virus or worm, because the computer used to slow down extremely bad while using internet. But a lot of scanning showed no result. Soon, and i mean soon, my computer stated to hang (offline), and sometimes, I don't even get the startup screen. It even hangs in the BIOS screen. My hard disk is almost 8 years old, so the question is, that is the hard disk's S.M.A.R.T signalling me something, or is the culprit something else. Can the RAM also be the issue, because sometimes, I have to remove my RAM, clean it and then again insert it, for the computer to get going.
Even after that, it would hang after 10-20 mins, or even less. Finally, my DVD combo is also around 10 years old, but I don't think that has anything to do with it. I am pretty sure there is no virus or any other malware.