You mean you have a hard drive partition called hdd5? You can use fdisk to do it from the terminal. Go:
This gets you into fdisk. From there you can use
p to list your partition table,
m for help, I think
t to change the type of the partition. You should use
l to find out what the numeric code for the partition type is. Once you're done with fdisk, write the changes and quit. Then go:
Code:
mkfs -t type /dev/hdd5
That's it.