All I could suggest is download the newest catalyst driver for your video card.
http://downloads.guru3d.com/download.php?det=1562
I had HL1 running in the pre-RC versions, so there shouldn’t be a reason why this won’t work.
Disclaimer: I’m not responsible if you computer explodes, catches fire, or some other act of god occurs resulting in a meteor blowing a hole in your computer, blah, blah, blah, etc.