I don't have CS 1.6 installed - I have CS: Source though. Once I bought HL2 steam screwed up my old HL and CS install, and more importantly, DoD:S.
I thought of reinstalling just for the ability to play the original DoD, but I decided to wait for the release of source. Which now, is going on almost a year since I payed for it and I still can't play it. Its starting to really annoy me.
JKF - If you can, I'd recommend trying out Day of Defeat. I liked it a lot more than counterstrike.
Do you have HL2?