Wait for a Steam sale. Counter-Strike 1.6 drops to $2.49. That is less than a coffee, and you get guaranteed online play, no viruses, and full access to the Steam Workshop for sound mods.

Download the archive and extract it to a dedicated folder.

Deep forum threads sometimes leak cracked versions of private cheats.

Scammers are clever. Here is how to avoid losing your time or money (yes, "free" hacks can still cost you your data).