I believe Vista will allow you to load mass storage drivers from USB flash drives or other CDs during setup.
For XP, you can slipstream the drivers into a custom XP installation CD with NLite.
you can also slipstream with vista using 'vlite'. it's similair to nlite but then for vista. there are also usb floppy drives on the market that are recognised as a normal floppy drive but you will have to google for it