Hi again,
It seems strange that everything was working OK but is now causing problems and the obvious thing to look at, would of course be the HDD.
Trying to install a Linux distro is a good idea as, if you still have a problem, you know it is probably hardware rather than the OS causing the problem.
As a matter of interest what other hardware do you have installed on your system apart from the items you have already mentioned?
Also, are you overclocking anything?