It sounds as though the drive doesn't have an on-disk partition table, so your Xbox is forced to use the default behaviour of your softmod to decide if the disk is F only (06) or F and G (67). It's easy to change that default behaviour using the tools that come with your softmod - so for Krayzie NDURE 1.1.1 you use Krayzie extras. Load Extras, select "Launch Extras" - the LED will turn Red - select "Set nkpatcher.06" - "Set nkpatcher.06". Reboot, and you will have one large F partition.
To revert to the original behaviour, go through the same process, but select "Reset to nkpatcher.67".