Let me see if I can straighten a few things out for you.
Is it just me or does it seem like it's a little useless to have the partitioner in Linux for a Windows file system? Maybe it's there for show?
No it is not useless. Linux can partition, just as Dos can, windoze, OS/2 and the list goes on. Partitioning is setting up the limits in a table where the file system will exist on a drive. Every OS has to be able to do that. Formatting is another thing. Formatting sets up the file system to be used. Windoze supports NTFS, Fat32, fat16 and fat12. Linux has a much longer list. Ext2, Ext3, Reiser, fat32, fat16 fat12, and many more I have not mentioned. Support for NTFS is limited, remember this is a system owned and operated by Mr. Bill.
Fat support is there because this is a way to share for those who wish to. It is a simple system, that is well known.
So, after format I'll go back into Linux (which should recognize the partition already?)
Most likely it will be mountable and you shuold be able to read and write to it. Most distros have support for vfat in the kernel. If yours does, then you should be able to mount it, read and write to it.
Let me see if I can help you with mount. First of all you need a mount point in the existing file system. You create one with the 'mkdir' command. Linux is not windoze. There is one file system that can be on several disks, and many partitions on several disks. It starts at 'root' designated by '/. Most systems will have a /mnt directory. The leading / indicates mnt is one level from /, the root. So if you do a CD to /mnt, you are in mnt. This is a common place to add more partitions, whether they are on the same disk or another disk. To create the mount point, do a CD to mnt, and then do a mkdir command and call the folder that ever you like. (mkdir whateveryoulike) It would be represented as /mnt/whateveryoulike/ . This is the place where you wish to mount the new partition, in your case hda7. You can mount it one time using the mount command. If you booted after the mount, the fie /dev/hda7 would not be automatically mounted after the boot. You set that up in /etc/fstab.
The command is the partition, followed by the mount point, followed by options. You have to specify file system type. See man mount for more details. So, a command such as 'mount /dev/hda7 /mnt/whateveryoulike vfat' (without the quotes) should work.
To mount every time you boot, as root, edit the /etc/fstab file and add lines like I posted. The kernel reads the /etc/fstab file during booting, and tries to mount the file systems listed in fstab.
The end result if it is successful, is /dev/hda7 will be visible if you navigate to /mnt/whateveryoulike/directoriesonhda7/morestuff/ etc...