There are a couple of different apps that you can download that will show you your product key, just gogle it.
Hi, In trying to load a purchased program form disc I get asked by an MS dialogue box, 'please enter your w7 product key'  I purchased an Inspiron 1545 2 yrs ago, with Windows 7 pre installed, and can't find the key. There is no label on the computer or box. I'm looking for a 25 digit no. split into 5 5's. Can you help please? Thanks , Nick 
Windows 7 Product key