Again with the piracy first ask no questions attitude
There are many reasons for issues with activation that don't include piracy.
So what's the actual issue here firnas ? is this another OEM version of W7 that has decided to just display the message ?
Is it a shop bought package ? are we talking Home PC or laptop ?
Usually the product key on a PC is on the holographic sticker which will be most probably on the back of the case or with a laptop the underside or in the battery compartment.
Have you installed anything or un installed anything ?