Just delete both f and g back to unallocated space then reformate the drive however you like.
1. Back up any important data from the two drives first… there is software around that can repartition a hdd without formatting it first but I've not been overly impressed with any of the ones that work within xp.
2. Take a note of page files, recovery partitions or other hidden partition on that hdd?
3. Confirm that no folders (like my downloads) are being redirected to the F or G drive before you proceed.
p.s. yes, a primary partition within a drive can hold a boot section but doesn’t have to and in fact doesn't in your case, so it is just another storage drive.