It should be exactly like XP was from what i've read. I dont think its smart enough to realize whats been changed, it just knows the hardware profile string is diffrent. It will allow you to reactivate 3 times through the automatic activation, after that you'll allways have to phone microsoft and have them generate an activation code for you.

I've only ever had the one copy of xp and i've used it on 4-5 diffrent computers with many reinstalls.