As everyone else has said onboard graphics are going to be quite limited for games, they're intended primarily for web surfing, playing movies etc. If you have any interest in gaming get a discrete card, I'd go with a Radeon 4670 or better (start at $70ish on newegg) depending what your budget is you might want something better.
That said some radeon igp's have 'sideport' memory in addition to shared memory. If yours does there should be a bios setting to enable sideport only, shared only, or both. This can have some effect on performance, but regardless will not equal a real card.http://www.tomshardware.com/reviews/790gx-graphics-sideport,2088.html?xtmc=sideport&xtcr=2