Unknown video card problems

Alright a few months ago I had bought Left 4 Dead for the PC and the installing went alright. Steam runs fine but as soon as I went to play it, it says that my video card is unknown. I have no clue what to do... Do I need a new video card?

My Driver Details:
OS Version: Windows Vista
Description: SiS Mirage 3 Graphics
Version: 7.14.10.5052

I have no clue what to do and I tried to search up anything similar but there's no luck. I need instructions what to do because I'm so confused.

[Note: The opening scene works fine but once I get to the main menu it lags only a little but the other menus somewhat lag and the loading of the game and playing lags way too much then sometimes it just crashes and my desktop pops up again.]

If I need a new video card, how much [appox.] would it be?
 
Yeah that's an older graphics adapter, so all bets are off with driver support and newer games...

If you know what motherboard you are using, we will be able to point you in the right direction with buying a new graphics card, price is going to vary.
 
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