If you want a system that will run KOTOR well, you'd be better off finding an old XP system someone is offloading for next to nothing (or better yet, for free). Any new card worth having isn't really optimised for crusty decade-old OGL console ports.
That being said, you have a few options, although "cheap" is an extremely vague term. You might want to specify a budget. I would say an nVidia 560 Ti is about as entry level as you'd want to bother with. Anything less and you may as well stick with your integrated graphics, especially given how anaemic your CPU is (that will be a bottleneck in any modern game). Looking at the Newegg site, they would appear to be around the $200 mark, slightly less for ones with a mail-in rebate. Someone else may be able to offer their 2¢ on ATI/AMD alternatives, if you go in for that sort of thing.