I have used Gparted, Partition Magic, and the Windows management tools. Although I think you're making your OS partition a bit bigger than you need to. If you are just going to be installing Windows and your programs on that partition and your documents folder, files, etc on the other drives you shouldn't need such a big partition. I usually use 20-30gb.
Many times when you've installed windows and it boots up for the first time, you'll see the unpartitioned drive sitting there under "My Computer". If it does show up you can just right-click/format and choose NTFS. I like the Gparted live CD, it's very easy to use and works great. I like partition magic too, though.