The manual for the Asus Pundit-R (contains the P4R8L mainboard) is available at support.asus.com as an Acrobat document (.pdf).
The ATI 9100 IGP graphics don't support Aero Glass, as others have told you.
If you desperately want that, you can add a discrete graphics card. It must be PCI (not PCI-Express). There are suitable cards based on the nVidia 8400GS chipset, for example.