Very large portion of this site's traffic is from users searching for cd keys for Windows Vista. However, as I mentioned in one comment, I cannot fulfill these requests. One simple reason is because I am not authorized to do that. However, there are many workarounds for extension of grace period for using Vista, and most part of them are based on using slmgr.vbs that is part of Windows Vista.
There is an excellent and comprehensive guide for speeding up Windows Vista. It is published on ExtremeTech. Here is a link: http://www.extremetech.com/article2/0,1697,2110605,00.asp
Of course, whatever you do, it's on your own risk...