If you are actually looking for the retro 2000s experience (Counter-Strike 1.6), it is still officially sold on Steam for a very low price. Purchasing it legally ensures you get a clean, virus-free installation and access to secure, active community servers. 3. Explore Community Mods
To clear up any confusion about which game you might be looking for, here is the official chronological order of major Counter-Strike releases: counter strike 14 cd key
To help you find the exact game you are looking for, here is the official timeline of mainline Counter-Strike releases: If you are actually looking for the retro