I purchased my HP laptop brand new back about 4 years ago. The HD recently died on it, so I purchased a larger HD and 2GB ram to give the thing more capacity and a little kick in the pants. Now I go to install windows XP using my windows XP Home disk (rather than the HP recovery disc crap which puts a bunch of other stupid programs on my computer that I don't want, and uses a total of FOURTEEN CDs to reinstall everything to original specs). When it came time to enter the WinXP Home product key, I assumed that the WinXP key provided with the laptop would work, but it did not. Says it's invalid. I copied it verbatim off the sticker on the bottom of my laptop. No go. Are OEM WinXP installations somehow mated to the hardware the laptop came with? Since the OEM HD died, I had to replace it, and chose to upgrade it. Is this what's causing my "invalid product key" issue?