Need to recover my VISTA RC1 CD Key

First, should I even bother. Will Microsoft even authenticate a new install of VISTA RC1 any more?
Next. I have since changed my motherboard so naturally the exixting installed VISTA copy on that HD won’t boot. And of course I can’t find my CD Key / COA. If I can’t boot I can’t run Regedit to poke around and get it back. What is the usable work around? TNX. Hz”