Stretch desktop across multiple video cards.

Using Windows XP Pro. I want to know if I can install 2 or more video cards
(PCI or AGP + PCI) and stretch my desktop across them. The effect I am
looking to achieve is a video wall where my desktop (or application window
that is running) stretches across all monitors to look like one large
monitor. In addition, if I use video cards that have dual or quad outputs
on them (say a Matrox of nVidia) can I additionally have that card stretch
it's input onto it's two/four outputs? For example: Two quad cards
connected to 8 monitors in a 4x4 configuration with my desktop stretched
across all of them.

TIA