If you decide that's what you want to do, you'll need either your Vista DVD or the system restore disks that came with your computer. Just insert them into your drive and reboot. When the startup splash screen comes up, you might have to hit either F8 or F12 (depends on your hardware) to go into the BIOS settings and tell the machine to boot from the DVD drive. The reinstall should walk you through it from there.

Good luck!