I know this is kinda old but I just found this thread. Microsoft doesn't like you taking a drive from one computer and putting it in another. Best bet is adding it as a secondary drive and backing up what you really need. If your computer craps out and is more than 3 years old it's probably better to replace. Windows 7 ROCKS! Many people don't know this but, If you have the Ultimate or Professional versions you can download virtual machine and XP virtual mode. So if got stuff that still needs XP or 32-bit OS you're good to go. You need a PC that supports VM so if you have a bargin PC it probably won't work. I've got a quad core and everythings just so nice. The new icore cpu's kick butt if you're shopping.