You need additional RAM for starters. I would recommend a minimum of a gig of RAM, 2 gig would be better. Since you are running a socket A, you will need DDR RAM. DDR ain't cheap anymore, a one gig stick is around $45, and a set of 2x1 gig is $95.
A better GFX card would be a boost as well. If you are running a 4 series, you are riding a dinosaur. Today's onboard graphics would run better (tough, but true). A dirt cheap card would work well for you, such as a 7300 or so. Try to avoid those that use system memory (at work, or i would provide links).