What you should have done before downloading the demo was to check to see if your computer met the specifications of ALL the requirements for JK2. Because with the newer the games, the bigger the demand for high-performing video cards. And your SiS video card is probably an integrated one, (built onto the motherboard) which games like Q3 and Jedi Outcast give a run for their money. Jedi Outcast is a farily high maintanence game with graphics.
I know i've seen somewhere that will allow Jedi Outcast to run in D3D (Direct3D) and it having to do with some command parameter, but the command is escaping me.
Shut yo face before I punch you in the mouth, break your teeth and call you Snaggle-tooth.