Gremlin had the same problem, which he mentioned in his review.http://www.gameboomers.com/reviews/Jj/JackKeane2/JackKeane2.htm
Make sure, whatever you do, that you update your PC's video drivers to the latest available from your supplier, and ensure you have the most up to date version of Jack Keane 2 as well (easy if you use Steam, because they'll do it for you) because the initial release, via Steam in particular, had a show stopper of a bug which meant that the frame rate (speed of animation) was atrocious, rendering play impossible.
But his card is a Radeon HD4670 512MB -- a lot faster than yours, and the minimum Nvidia spec for the game is Geforce 8600GT, also a lot faster than yours. Also, I couldn't find any patch or update for the English version. I assume you'd have to contact either the company that developed the game or the company that published your disc version to get them to send you the patch.
If you want to replace your video card, you'll probably have to replace your power supply too, and possibly add a case fan. Faster cards require more power and create more heat. Without knowing more about your model of computer, it would be guesswork what would work or not. But if your computer came with a Geforce 6200, it might be time to start thinking about a new computer. The Geforce 6 series came out in 2004 and was replaced by the 7 series in 2005. So I imagine your computer is getting a bit long in the tooth.