There are two places at least where ProductId gets stored. To see the first place, open Registry by going to START-RUN and entering REGEDIT and Navigate to
[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\ Windows NT\\CurrentVersion]. In right pane,
look for key by the name "ProductId". This is your Windows Product Id. Alternatively you can navigate to [HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion] and still find same field with the name ProductId.
