You can install one (1) copy of Windows XP on one (1) computer.
A second installation requires a second license (Product Key).
In other words, you need an individual license (Product Key) for
each installation of Windows XP on a different computer. That
means you need to purchase two (2) licenses (Product Keys) so
you can install Windows XP on your two (2) computers.
Go to Start > Run and type: WINVER , and hit enter.
Then click on "End-User License Agreement" for clarification.
You can also open XP's "Help and Support" and type: EULA
and hit enter. Click on "Questions and answers about the EULA".
Additional Licenses for Windows XP Home Edition
http://www.microsoft.com/windowsxp/home/howtobuy/addlic.asp
Additional Licenses for Windows XP Professional
http://www.microsoft.com/windowsxp/pro/howtobuy/addlic.asp
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Carey Frisch
Microsoft MVP
Windows XP - Shell/User
Be Smart! Protect your PC!
http://www.microsoft.com/security/protect/