I had an interesting thing happen to me when I tried installing CentOS 5 on VirualPC 2007.

Currently RedHat and SuSe linux guests are supported by VirtualPC. Installing other linux guests is possible. To install CentOS 5 as a guest in VirtualPC you will need to install it via text mode. If you try to run the setup normally, you get wierd graphic issues like the one posted below. This is due to the fact that it does not understand the graphics chipset that VirtualPC uses.

CentOS 5 graphical installation on VirtualPC 2007

To get into text mode in CentOS 5 at the boot: prompt type in linux text

To install Ubuntu 8 and later on VirtualPC you will need to run the installer in SafeMode.

After that, its pretty much straight forward.