hey, im running source perfectly on my toshiba laptop with incredible graphics, my video card is a geforce go7600 256mb. what is your graphic card exactly, update your card with the latest driver and go for a modded (tweaked) driver which will always improve the performance and quality of your card. what kind of error you getting?
I'm having similar problems with this game, and Fable too.
When I start playing, it's allright, but then, like in 3 to 5 mins, it starts to lag, the fps go down (from 60 to 15, for example), and if I close the game, and I run it again, its does the exact thing over again.
My PC is:
Motherboard P35Neo MSI
Video Geforce 8600 GT XFX
HDD Hitachi 320Gb Sata
CPU Core 2 Duo 2.3 Ghz
I tried went back to older drivers from the graphic card, but it's the same. And this worked perfect yesterday on Vista... Everything else works fine.
Note: I did an upgrade, not a fresh install. If an upgrade it's not safe, it shouldn't even be there.