Windows boot up error

Its hard to say when my problem began or what happened so I'll start at the beginning and make it as brief as possible.

About a month ago I upgraded to 1GB of ram. About a week or two later I started getting artifacts, so I checked and my video card was overheating. So, after installing a new heatsink the temps went back to normal.

Then, about a week later weird things started happening...a couple boot problems at startup, but once I hit reset they fixed themselves. And then one day, WoW froze. Upon restarting I was given an error saying that a file was missing or corrupt (I think it was the config file in system). And so I decided it was time for a fresh install anyways so I formatted and whatnot and it worked great for almost a week....and now it has happened again. I can't boot because:

"windows could not start because the following file is missing or corrupt:
<windows root>\system\hal.dll"

I can't get the windows CD repair to work however, so I'm at a loss as to what to do. I ran CHKDSK and it said there is 1 bad file. I don't know how to use the recovery console to fix the file though...and if I do, something tells me it will happen again anyways. Is my harddrive shot?

Any help is greatly appreciated.

P.S.: sorry for the long post.