To check whether your windows XP is already activated,
 
open the Run dialog box
Type: oobe/msoobe /a
Click ok.
 
If your copy is activated, you will be greeted with a “Thank you” screen; if not you will be prompted to activate Windows.
 
To ensure whether your copy of Windows XP was legally purchased, use Microsoft’s online validation process here: www.microsoft.com/resources/howtotell/
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