Install R2 VLK on 2003 SP1 non VLK

I have a client who is running 2003 SP1 with a non volume licence key
(possibly OEM) they have purchased 2003 R2 VLK licence and media but when I
tried to install the R2 cd using this new key it does not accept it.
Anyone have an idea of how I can avoid a system rebuild?

I found the following answer but want to know if anyone has done this and had
any issues:
you need to upgrade your existing instalation using R2 CD1, and use your VL
key, and then you will be able to use CD2 to install R2

"ozi83" wrote:

> I have a client who is running 2003 SP1 with a non volume licence key
> (possibly OEM) they have purchased 2003 R2 VLK licence and media but when I
> tried to install the R2 cd using this new key it does not accept it.
> Anyone have an idea of how I can avoid a system rebuild?