Half-Life keeps closing

I managed to come across my old copy of Half-Life the other day. I also found all of the expansions to go with it (counter strike, blue shift, etc.). Everything installed properly, and boots up just fine. But when I was playing Blue Shift, it only let's me play for a bout 5 minutes before it freezes, and then goes back to the desktop. Haven't tried counter strike yet, but Half-Life itself plays fine (btw, this is the original Half-Life from 1998). I have already set it to compatibility mode for 98, and reinstalled the game. What can I do?

I don't suppose registering it on Steam is out of the question?

didn't think about that... It's worth a try I guess
OK, steam didn't work... but I did find out my problem
I had to go into the video options and switch it to Direct3d from software mode