Graphics have jerky movements

[MarleneD]

My son has the game Call Of Duty (first one in the series) and while he's playing it sometimes the characters start to  be less smooth and then have "jerky" movements; also, the sound sometimes lags behind the action.  Could it be that we need to get a larger memory video card?  I've recently installed Windows XP on the computer and placed it in his room.  It is not connected to the internet.  I've downloaded the NVIDIA drivers and installed them on the computer.  
If I do need a new video card, which ones should we consider?  Thanks  

[Fed]

You need to Google for the game's minimum & recommended specifications.
Then see how they compare with your computer specifications. Download & use Belarc Advisor or Everest Home Edition to find what your computer specs are.

[Raptor]

What are your current specifications?

I used to run the game,rather smoothly on the following specifications:

1024MB DDR RAM
128MB ATI/Raden 9000Pro
40GB Seagate 5200RPM
AMD Athlon XP +2600 2.1Ghz