As almost always installing a second windows installation next to your primary seldom goes without a hitch. If you ever want to install a Windows 2003 next to your already installed vista than have the install disk of Vista in hand.
I had to use the command prompt to start Bootrec.exe and rewrite the boot sector. After that I had to download Vista Boot Pro and add Windows server as an install entry. Finally after three hours of hard work and searching the install could finalize.
And now for the rest of the server installations.