Right, first of all why do you want to uninstall redhat?
if you're quitting why don't you ask for help with whatever the problem is?
Or you could be a student wanting to play a very nasty trick on your linux-using flatmate
If this is the case then you are going to get battered.
---- The Answer ----
well, if you want to have some fun before doing the real work you can make sure all your other partition(s) are unmounted (type "df" and see what is there) and type "rm -rf /"
and then run partition magic and resize ur windoze partition, or run fdisk and make a new one.
And i think you can reinstall the windoze MBR with the recovery tool (you type "fdisk /mbr" i _think_)