That happened to me simply because I forgot to activate it. I had to phone MSFT and get instructions to enter the activation number without having to reinstall XP.

Also, I did the same thing. I moved a copy of XP from one machine to another and I had to phone MSFT to manually activate it again. I received a message that the copy of XP was already activated on another system and to phone MSFT and it provided a 1-800 number to call. The system would completely just shut down. It appears that there may be specific hardware difference (motherboard type perhaps or different hard drive) they are looking for.

>That's interesting. My understanding is that an unactivated machine will "self-destruct" in some manner at the end of the grace period ( ~30 days? ).
>
>>I have an xp machine in here but have never activated it, its running about 18 months with numerous restarts and never a problem. probably jinxed myslef now:)
>>Slán
>>~M
>>
>>>I recently upgraded my main home machine from WinXP Home to Pro. This leaves my XP Home version eligible to install on my secondary machine which currently has Win98SE on it. Question is, how do I "deactivate" the activation for the computer XP Home was on so I can apply the activcation to the second machine since MS will reject the attempt to activate XP on the second machine due to different hardware, etc. Is there a procedure for this? Does MS have to be contacted, etc.?
>>>
>>>Thanks,
>>>Bill