I recently bought a new computer and there was no sticker on the computer to tell me what my Windows 7 key codes were.
Belarc Advisor is a small and easy download which will run and tell you all of your hardward configurations and also all your software key codes. After you find the codes just do a copy/paste it into a secure space.
It also shows you the security fixes you need.
Note – check the codes that Belarc gives you against the codes that might be on the sticker that is on the computer – they may be different.