You can run fdisk or cfdisk when you log in as root. Type
'fdisk /dev/hdc' and you are there. It is pretty easy to use fdisk, but the partition schemes are diff. than in windoze. The primary master hdd is hda, the primary slave is hdb, the secondary master is hdc, and so on. So, if you want to change the secondary master, do
Then type p, and you will get the partition table. Change it and you are done. Don't forget to save the changes when you come out of fdisk.