Last I knew MS wouldn't tell us exactly how they determine that a system had changed too much to be the same system. I've read it is a combination of quatifiable and identifiable components such as CPU ID, NIC MAC address, HD serial number, BIOS info, video adapter info and more. I did read a series of postings somewhere saying somebody changed the IO channel of their Vista boot drive resulting in a request for reactivation and changed te channel back to fixed it. This was confirmed by another user.

On XP I know I could change about anything as long as I didn't change too many things too close together in time. On XP I've replaced the video card once, the boot drive twice and the network card once without trouble.

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>My understanding of this has always been fuzzy. What defines THAT system? The mobo, cpu, hard drive, case? I haven't ever been able to find a definitive answer.