well. people will want to know what monitor resolution you want to play at and what level graphics you find acceptable (low medium high). what motherboard you have would help.
my initial thought is you may need to start from scratch if you want to game, but COD isn't that demanding so maybe something can be done. someone with more experience with older Intel systems may have a better idea. here are the cod blackops requirements though.
Minimum System Requirements:
- OS: Windows Vista/XP/7
- Processor: Intel Core2 Duo E6600 or AMD Phenom X3 8750 or better
- Memory: 2GB
- HDD: 12GB
- Video: Shader 3.0 or better 256MB NVIDIA GeForce 8600GT/ATI Radeon X1950Pro or better
- Sound: DirectX 9.0c-compatible
- DirectX: 9.0c