I cannot log in to my Windows 7 account.

I cannot log in to my Windows 7 account. My wife accidentally changed my login password and now I cannot log in since I don’t know the password and she forgot it too. The problem is I have been looking around for the installation CD and just couldn’t find it anymore.

I need this to reinstall Windows 7 to reset the current configuration. I don’t want to format my hard disk because I have so many important files on it. Is there a way to access my computer without my user password and without using any installation CD?
