drivers for sis 5511 or 5513

Two years ago, I bought an Hp Vectra series 500 Model 320.5/133. I had to reinstall the operative system (Win 95) but I found out that it din't recognize the video chipset integrated on the motherboard. Hp assistance refused to help me. Opening the case, I discovered two integrated chipset made by SIS. One was the 5511, the other was the 5513. I think that one of these two is the graphic chipset, but I couldn't find the proper drivers. Can somebody help me?
Thanks.
Alex