Use the utility QTparted off the "K" menu. It's a GUI frontend and should be intuitive. From there you should be able to remove any remaining MS partitions (save between steps to actually commit the changes) and recreate the partition structure you want. Since you're going to reformat the drive in preparation to install Windows the format of the drive should be irrelevant but, to be safe, use FAT32.

HTH,

'Goon