Can you tell me if it has an expansion slot for a video card?
Since you found the link to the support page you should be able to find that out on your own. Your homework assignment is to download and read the manuals, then report back with the answer you find. If there is a slot, for extra credit please tell us what standard it follows...
The PC in question has no expansion slots, parallel port, or SCSI ports.
I will unfortunately have to give you an "F" on that assignment! According to the Hardware Reference Guide
it has 2 expansion slots, one is MXM
(Mobile PCI Express Module, for video), the other is PCIe Mini Card
(Mini PCI Express, primarily for wireless adapters).
Would it be better to install XP or Vista on it?
I would install which ever OS you have available for the lowest cost and are most comfortable with. Scott.