Have you already installed or are you trying to install?
Assuming you installed without a key and now you want to enter the key to
activate, did you do an actual upgrade or a clean install? Also, what type
of package do you have, Full, Upgrade, or OEM?
Do you mean the Product Key: 5 x 5 sequence of alpanumerics?
This Key is typically not on the CD, but on a label attached to the DVD box
or on the purchased machine.