How to delete call of duty black ops?

So iv'e been trying to reset everything for call of duty black ops as my perks are glitched in combat training (can't get pro version's) and i can't figure out how to do it. I deleted all call of duty data(except map pack) on my xbox hard drive but i still have my rank's and such. Does anyone know how i can delete all of it and start over? I thought everything online was saved on your harddrive but apparently if you delete it it keeps it? I just really need some help.