Exactly the same way you installed it in the first place.
I assume you mean product key, not product ID.
If you have lost your product key - you can find it with the free version of SIW:
D/L the Standalone - second down on the left.
Rt click it, Properties>Unblock>Apply>OK.
Rt click and Run as admin.
Click Licenses in the Left pane.
Hope it helps.
Quote: Originally Posted by horeen
how i can ReInstall Windows7 useing my Product id
my oc is
win 7 ultimate full