You can see that the 8400 is way down on the chart, even below the onboard graphics alot of motherboards have. Its not designed to run games.
It should play flash games and such, but is not likely to play any heavy games like COD or MMOs like WoW even at minimal settings and low resolutions.
Something like an ATI 4650 or 4670 should let you play most games reasonably well at low resolutions. If you want to play the latest games on newer HD LCDs you would need a new computer and expensive gaming card to have a good experience.