You may install/reinstall Windows XP as many times as you wish
as long as it is reinstalled on the same computer. If you wish to
install Windows XP on another computer, then you'll need to purchase
another license (Product Key).
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Carey Frisch
Microsoft MVP
Windows XP - Shell/User
Hello
There is no limit on how many times you can install XP.
There is a limit on how many times you can activate XP without calling MS.(1
every 120 days)
There is a limit on how many computers you can install XP on with the same
key code. (1)