In Cs 1.6 you can actually use the -dll parameter to specify the dll file to load.
also what the error message exactly is, and what the Dr.Watson reported ?
More about the "illegal" thing: Unlike previous versions of HL/CS, from CS 1.6 Valve used a strict DRM (Digital Restrictions/"Rights" Management) system named "Steam" which requires you connect to the Internet when you want to run the game, so that they can effectively control the game from being copied unauthorizedly. You can still run the game in LAN though, but you must use the Internet to get the Steam, and if the version you've got is not via Steam, it will be illegal. I don't think that's wrong or bad though, but you had better not to do so as you'll get into trouble - the above one is still a "small" one
"It's time to write Valve a letter" - well they will simply ignore you