Studio XPS 1647 - graphics

Hi!

Wondered if any one could help me out im trying to find out whether or not i can upgrade the graphics card in my rig. My current specs are:

i5 540M 2.53GHz

500gb HD

4Gb RAM

Radeon HD 4670 1Gb

Basically i want to know if i can swap out the Radeon HD 4670 1Gb for something better because there are a few games i can't play as the gpu is on 100%.

Thanks, E