Dual booting FreeBSD and a system containing an NT based OS is really trivial if you install FreeBSD on the same hard drive as you boot NT from. I do not have an NTFS c-drive. I depend on space being available to exchange data and you can 't do that if your primary boot partition is NTFS. It doesn't matter if it is FAT16 or FAT32 but it needs to be one of the two. My typical c-drive is 2-4GB and FAT32.
There are a few things that you need to have available before you start the install. For example, you need something to do a simple boot to run fdisk. I have a Win-ME setup disk that I use for that purpose. You install FreeBSD. The install, regardless of what you tell it, will set the active partition to the one containing FreeBSD and they claim Microsoft is ego-centric. You have to set the active boot partition back to your c-drive with fdisk on the "startup disk", add some simple changes, and it works. The simple changes amount to you copying /boot/boot1 onto your c-drive. I call it bootsect.bsd.. Then, you edit your boot.ini to include bootsect.bsd as an option. As an example, you can see my boot.ini from opal. The whole process is really pretty simple.