How to Disinstall DLC on the PS3?

One of my friends came over to my house and logged in on his PSN account. He apparently downloaded his fallout new vegas DLC and his call of duty black ops dlc on to my ps3. He downloaded black ops which had me upset, cuz i love to pwn me some n00bs. With the map packs, i play against people who ren't n00bs because no n00b buys $15 map packs! I want to disinstall the black ops maps WITHOUT losing my fallout new vegas DLC... ANY HELP?!