VISTA SP1 Evaluation Copy Upgrade

On a previously registered copy of VISTA Ultimate, I installed an evaluation
copy of Windows SP1. In the bottom right part of my screen, it states:
"Windows VISTA (TM)Evaluation Copy Build 6001." Now, many months later, I
have begun getting balloons that my evaluation copy is about to expire, and I
need to install any version of Windows VISTA. I REALLY do not want to do a
clean install, or loose any data or programs. Can anyone please tell me what
the procedure is?

Many thanks,