The first was on my own totally rebuilt (from an A64 to a C2D setup) system using a legit copy of XP Home upgrade that was originally activated in March and hasn't been reinstalled since.
It installed and activated fine, but when I pulled out my secondary DVD burner to make room for the SATA burner arriving in the mail this week, I got a 'Windows has detected significant hardware changes and needs to reactivate'.


The second was on a system for a client using a legit, unopened copy of XP Home upgrade.
After the initial install, he decided that he wanted more RAM and a different brand of DVD burner.
I installed the memory and it ran fine.
The next day I got around to swapping out the DVD, and got the same message saying that 'Windows has detected significant hardware changes and needs to reactivate'.
WTF is this shit?
After speaking to a phone drone in India, I reactivated the client's machine with no problem.
I'm waiting until the SATA burner arrives before I reactivate my own.
If this is how WPA works, no wonder XP piracy is so popular.