Re: Keeping hard drive
For legal purposes, you're suppose to buy another copy of Windows XP but come on, who really does that? I don't. The only thing that I can think of is some things might not work. PC may not boot or it might. The original hard drive has installation files related to the hardware of your old PC which may create big time conflicts with your new setup. I would do a clean installation of Windows XP on the old drive. If your old PC came with an OS CD, just use that. The operating system itself may also be on the recovery DVD but I don't know how to extract that. You can probably try to find the OS by browsing in the DVD, but I don't know if it's slipstreamed or all bundled up everywhere.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?