Windows XP Pro legit key sharing.

Can a Windows XP Pro legit key be shared between two people safely. Or will MS blacklist it.
Wanted to know about this because I was thinking of asking around for one and didn’t have much to give away in return. That is provided legit key sharing in XP is allowed to some extent.
Answer #1
Well it’s possible to activate more than one PC with the same legit Key…But the trick is if more than one PC try to do updates with the same key…It will be detected and maybe even blacklisted…
Answer #2
Thanks for the reply .
By activation you mean the serial we enter during windows installation?? If yes then even a non legit key can activate XP, isn’t it? It’s the updating that matters most..! Sorry, don’t know much about XP since I have been using Windows 2000 pro till now.
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Answer #3
Nope…You can’t activate without a legit key…You activate online…And Microsoft check if the key is in their database…you can install with a non legit key and then use a genuine activation crack….