Inspiron 8600 running Programs run slow

I have an Inspiron 8600 purchased in 2003, start noticing that when I attempt to do any type of browzing on Internet Explorer or Mozilla, performance is extremely slow. A friend mine at work stated that I probably need to upgrade my Video Card. I have a Nvida 64mhz, I tried to see if there was a 128mhz, 256mhz, or 512mhz, but the only ones I have found are for Desktops.

My harddrive has tons of memory (I have cleaned out all unused programs), I have defragged, and have cleaned out temporary files. The system still runs very slow.

Does anyone know do I need to update the drivers? is there a driver that is more than 64mhz? (hopefully I know what I am talking about or have explained correctly).