I haven't tried this myself yet, but here are instructions on how to setup an ultra fast USB flash drive with the Vista's installation files. You will then be able to boot and install Windows Vista to your computer from the USB flash drive.

This all sounds like a great idea for a tech support person. Microsoft seems to like the Apacer 4GB Handy Steno USB Flash Drive HT203, 200X Hi-Speed USB 2.0 due to it's 25 mb/sec read rate and 14 mb/sec write rate. These also make excellent drives for Vista's ReadyBoost technology, which can improve your computers performance. If you are lucky enough to find them in stock, you can order one for $56.99 from directron.com. Good luck on that.

Here is the link with details instructions on how to format, partition and copy the necessary files from the install DVD to your USB drive.