Type the following at the command prompt (Start> Run>cmd):

"convert c: /fs:ntfs"

(w/o quotes)
where c: is drive you want to convert. It'll run when you next restart.

To repartition you can use fdisk, which erases all data on your hd in the process or PartitionMagic which erases about $80 from your bank account (: There are some cheaper (free?) partitioning utilties out there, I think, but I haven't used them so couldn't recommend. Good luck.