You also need to initialize the drive in "Disk
Management" - If you can't see the disk at all in "my
comp." but can in "device manager" this is probably your
problem.
You do of course realise that the slack space on a 200GB
partition is going to be tremedous?? I'd seriously
consider splitting it at least 4 ways - but thats just me.
Anyway - Right click on "my comp." and pick "manage" to
get to "Disk Management".