Half-life and opengl...

I have a pretty old pc(win98,graphics card is rage pro, 64 mb ram, amd k6-2). I have updated my drivers. Software mode is really bad for me because after about 10 minutes of playing the game, it slows down and is hard to play. Opengl mode looks alot better and plays faster too but it always freezes after awhile and I have to restart my computer! Oh and direct3d dosen’t work very well because the sound is bad and it freezes more frequantly then in opengl.

Is their anything I can do to stop it from freezing all the time?