Symptom:
When launching Gnome desktop on a virtual machine running inside Microsoft Virtual PC, the display is corrupted making it impossible to work with.

Solution:
The default bit depth used by Gnome Desktop is 24 bits while Microsoft Virtual PC only supports 16 or 32 bit display. To fix this in Centos 5 it is necessary to edit the Xorg.conf file and set the bit depth to 16 bits.

To change the bit depth:

1. Boot the Centos VM in VPC to the command line and log in as the root user
2. Edit the /etc/X11/Xorg.conf file
3. In the “Screen section”, Change DefaultDepth to 16
4. In the “Display” sub section, change Depth to 16
5. Save the file
6. At the command prompt type startx

Gnome desktop loads displaying correctly.