|It's not necessarily the hard disk, but if you are experiencing the same kind of freezing after wiping the OS clean then the problem is likely a hardware issue.|
Does the computer stay on long enough to boot it up, go to start, control panel, administrator tools, event viewer? If you can take a look for Errors in the system log. See if any of them look related to hardware.
Something else you can try is testing the RAM memory with memtest http://hcidesign.com/memtest/