What?! Is that possible? Yes, it is, I found out the other day. I’ll try to put together some kind of short guide, and see if I can get the facts straight.
First of all, visit the FragBase homepage and download the Non Steam CS 1.6 GAME and the Non Steam CS 1.6 PATCH. After downloading and extracting, run the .exe file, running the GAME first and then the PATCH. During the installation you might be prompted with Retry, Cancel or Ignore messages, make sure you just ignore them. Also, if you’re running a non-English version of your OS some text might be shown as question marks.
After installing it and running for the first time you might want to change options such as your name and your spray-tag. When you’re ready to play, you’ve got a job ahead of you – finding servers. Naturally you could try clicking Find Server and try joining, however you will not be able to play since you will be kicked for an Invalid CD-key. Finding non-Steam dedicated servers can be a hassle, but Google is there for you, as well as the FragBase homepage. The latter has three dedicated servers running (18.104.22.168:27015, 22.214.171.124:27015 and 126.96.36.199:27015) which you are free to connect to and have fun with.
Remember, this is most likely classed as illegal, and all of this is done at your own risk! Other than that, there’s not much more for me to say. Good luck and have fun!