Xero is right, it is pretty much impossible to upgrade the video card on your laptop. Because you already have the integrated graphics, you don't have the optional connection for a "stand alone" card. The only way for you to expand your options is to replace the motherboard, but I'm sure that's not feasible for you.
Upgrading a laptop is MUCH more restrictive than a desktop if you haven't noticed by now
You COULD upgrade the processor (which I think goes up to 2.2 GHz), but I'm not sure how substantial the difference would be.
You could also just upgrade the RAM up to 4GB.