Just had the same problem. Here is a short diagnostic worklist where it is going wrong. After each step try doing something that would normally cause your computer to freeze. In my case it was trying to copy files over my home network, but it could freeze at any time tho.
1: Unplug/deactivate all unnecesary peripheral devices from your computer. (note: network, modem, sound, printer, television, bluetooth mouse, and all other usb devices)
2: Replug/activate them one by one to rule out involvement. (note: when a device causes your computer to freeze it can still be software related, so reinstall drivers first if the device gives problems)
3: Unplug/switch/replace RAM. (note: replace means borrow from someone
)
4: Unplug unnecesary drives in your computer (note: DVD drives, etc)
5: Test/replace powersupply. (note: don't remove any hardware from your computer, just plug in the powercables in your motherboard, cpu-fan, videocard and primary HDD after unplugging the current powersupply)
6: Reinstall windows.
7: Test/replace harddisk. (note: this takes a while, so make sure you have a few hours atleast)
8: Cry because you have a major problem, atleast I would. (note: I guess your motherboard is not functioning properly anymore)
Good luck,
STuFF
I really hope this helped finding the problem
