A lot of prebuilt resellers are doing the whole "we're not offering Windows whatever drivers" hogwash on their websites, even if the hardware itself is compatible. I've found this with my laptop (Asus F3 series) and with my gaming rig (Asus M2N SLI Deluxe).
Usually, however, if you find the manufacturer of the hardware component itself, you can find some generic drivers or manufacturers drivers that will function.
Considering that Dell has a "switch to XP for $50" option on a lot of their desktops, I imagine you shouldn't have too much trouble.
As for your video card, there are a few sites that specialize in making generic drivers for mobile chipsets. The problem with mobile chipsets is that often a vendor will to lock you into using only their drivers, rather than the OEM drivers from ATI/AMD or Nvidia. That's why those third party sites exist.
I'd worry about the other components of your laptop more than the video card.