dell oem windows installed on hp (repost)

I posted this in gen. earlier, maybe should have posted here:

My 12 yr old daughter got our handmedown hp machine (pavilion 531w). It was running slow so I told her I would run a recovery and reinstall windows xp (from partition). Being a bright child and very independent she got tired of waiting and got my dell oem windows (home) cd and formatted and installed it on her hp. The recovery disc for the hp wont install from the partition now, and I dont want to give up my dell activation number. Any tips on how I can get the windows on the hp to load from the partition?

Get HP to send you and actual install disk? Ye, HP suck just as much as Dell.