The video in the introductory screens to united offensive seem to run ok, but the sound is choppy. Not really an issue - I don't care about these portions of the game.

However, I got about 30 minutes into the game, into a situation where I'm doing rapid fire machine gun work, with lots of other movement on the screen, and the sound and video get so choppy that the game really doesn't work well at all at this point.

Any advice would be helpful.

Thanks

More often than not when the video or sound begins to get choppy, it is a hardware related issue coupled with heat. While this particular game may run on a relatively lowly appointed machine, most of these games tax the processor and the video card so heat becomes a factor after a while. What is the hardware you are using and what video card do you have installed?