Maximum PC

Hey guys,
When playing games such as GTA 4, I set my graphics to their highest limits, and max out the 1GB of video card memory. The issue I have is that the shadows and shades in the game anywhere are not...solid? If thats the best way to put it.

Imagine looking at your own shadow on the ground on a sunny day...should be one solid shade throughout your shadowed figure, and have sharp defined edges right?

Now...If you're in GTA 4 (on my computer), the shadows casted are very GRAINY. (Is that a word?). It's like looking at the shadow of a thick bush that allows small bits of light through and onto the ground.

Is this a driver problem?
Thanks

Do you have AA and AF on? That may help sharpen up your shadows some, but it will take a toll on your videocard.