You can uninstall GRUB, which should then automatically default to the Windows Boot Loader; if it doe snot, you can replace it by running Startup Repair from your Windows Vista DVD. Once that's done, simply delete the files on that partition and either continue using it as is or repartition it using GParted (freeware).
Hope this helps,
John
alright,so about a year ago i installed ubuntu and gave it 80gb of my hard drive. Windows Vista is my main OS and i want that 80gb back from ubuntu. How would we go about this?im tired of my GRUB loader

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic