Black ops is cpu intensive and a bad port. You need to OC your cpu and get it to above 3. 3.5Ghz will do.
I suggest you get a aftermarket cooler if you don't have one.
Then you need to install all the patches for it as well.
Did you clean out the old drivers and updated the drivers?
If he was able to run the game in vista then how is tha he needs to oc his pc? I don't agree. Vista consumes a lot of resources, it should be smoother in 7.I can run BFBC2 on my pentium D.
Are you playing wireless online?
Are you closing your av or firewall or any p2p sw?