From Mr Teo En Ming’s personal blog and xen-devel mailing list:
I have made and uploaded a two-part video series on VGA pass through to Windows XP HVM domU to YouTube.
Here are the YouTube links and videos:
Basically Windows XP guest operating system has direct access to PCI Express x16 graphics card but in a reduced functionality state. The videos show that the passed through display card cannot found enough resources it can use. The device status for nVidia Geforce 8400 GS on my Intel Desktop Board DQ45CB is: