What Micheal said - you want it set for at least 256 MB memory or 512 if you have 2 gig of system memory. If you are lucky the 6150 has dedicated on board memory and this does not apply.
Next turn off Anti Aliasing (AA) and Anisotropic Filtering (AF). Leave them off, they are only useful on mid range to high end video cards ($200 and up)
In game -
Start at low settings for textures, and turn off lighting and shadow effects. These make good visual candy but really overload the video card.
Reduce visible "distance" as needed. I'd guess no more than 80% with on board. Note this hurts for FPS type games. ( You can't see snipers etc.)
Now increase textures until frames start getting jerky. Then try turning on lighting and shadows a little at a time until things get jerky again.
If desperate decrease resolution to 800x600.