one of my computers here at the office regularly crashes to the point that the mouse cursor won't move... i'm talking three times in an hour. in it's current state, it's unusable because of the random freezes.

I've been assigned to repair the computer, and i've checked many of the obvious things, the power supply, the hardware memory, cpu heat/fan/heatsync, i've even gone so far as to remove all of the dust from the inside of the case.

does anybody have any other ideas as to what i need to check?