I thought i'd mention other things, system restore.
It can take at least 12% of your HDD space away! 200 * 0.88 = 176.
But then, the hdd's "capacity" is not always correct, i have an 80Gb HDD, and it only displayed as 60Gb, and on top of that, there was system restore taking 12% (i turned it down a bit).
The way i ended up fixing it was pretty stupid, i accidently tried to run a DOS partition program, and well, it fixed my hdd, but not to 80gb, but to 76gb, which is good enough!
Ph30nix!