Hi Umgumby,
Your computer will definitely play World of Warcraft CataClysm with no problems. It is not the case for Call of Duty: Black Ops though.
The AMD Athlon 64 X2 Dual Core 4200+ 2.21 GHz processor is below the Call of Duty: Black Ops minimum requirements.
The 2 GB of RAM meet the COD: BO minimums.
What exact ATI Radeon X1800 series graphics card do you have? Some are fast and some are slow.
You need to upgrade your faster processor in order to play COD: Black Ops. You probably also have to upgrade your motherboard to fit the new processor. Here is a combo deal I found for you:
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.564797