After reading this post, I thought that VMWare could solve this problem. So, I downloaded VMWare Converter and a 30-days-evaluation version of VMWare Workstation 6. During setup of VMWare Tools on the guest OS a text message popped up saying, that I can get better graphic performance if I'd change something in the display properties. I was not aware of the described switch. Afterwards, there was a noticeable acceleration.
Because it was a windows internal property, I went back to my VPC and changed it there as well. The difference in Virtual PC was much more drastic. It solved all the performance problems I had. Now, I can work with the guest OS in a familiar speed. Finally, I was wrong and Virtual PC has no problems with Windows Vista as host OS. The pic below shows the the settings, which have to be made.
(Location: Display properties, tab Settings, menu Advanced)
