Yesterday I had interesting experience: I was trying to run Virtual PC/Server on Windows Vista.
After installing full IIS on Vista and turnning off UCA :) installation went smoothly. I copied esixting VHD with Windows XP SP2 on it and attached to newly created vurtual machine.
According Web-based manager and CPU meter Guest OS was started but... I see only black screen on remote client. From this point on I tried bunch of install/deinstall and so on. My friend Marto told me about existing beta of Virtual PC 2007 and I decided to give a shot.
After patiently register and download the installation package I installed it ... and ... can you imagine ... same nasty black screen.
As this is VPC 2007 is beta there is posts with bugs I looked at bug list. Lucky enough I found similar post which describe same problem and says... the problem is gone after restart or two.
I restarted my machine and THAT"S IT - IT WORKS :)
Probably I should mention I did all these efforts on laptop. Since I have the laptop I have used mainly hibernate feature and it is restarted only when MSI, OS or some software rewuire restart.
It is amazing how I forgot how good old restart resolves many many problems. I have been working with windows since windows 3.1 and used to know about magic of restart. Right now I am restarting less and less (and resintsalling my working machine very rarely)