I have had this happen twice. Set up a valid version of XP as a virtual machine and used it for days or weeks ( both ) then bring it up and it decides that there have been significant hardware changes and wants to reactivate with Microsoft. Why does this happen? Is there a fix for it? So far my solutions have been to either revert to an earlier clone of the same system or as in the most recent setup revert to an earlier snapshot. I'm really not interested in calling Microsoft to reactivate. Regarding the snapshot, it seems to be ok now that it is up. But I don't know that it won't do this again the next time I start up.