If wireless doesn't work, You have two options. The first is while on another computer, go to the manufacturer's website and download all of the drivers to a flash drive and then plug the flash drive into the Vista computer and install the drivers from there.
The second option is pretty much the same except using a blank CD and burning the install files to the disk (kind of a waste of a disk though).
This is all assuming that you don't have the original driver disk. If you do have the original driver disk pop that in and install the network drivers then go out to the net and get up to date drivers from the manufacturer's website.