My Diablo 2 game has been getting pretty laggy, what can I do to free video card memory space or whatever?

Im pretty sure it has to do with the graphics. I have a 128mb video card so i know its compatible and stuff for like a somewhat old game. What can I do to make it run more smooth?|||the game is old and the 3d featue is old|||More than likely it is some other program running that is causing the lag, such as a virus scanner or firewall. What are your other specs? The video card does not sound like the problem maybe the RAM.