In 2020, Rockstar Games replaced the original version of GTA IV with the Grand Theft Auto IV: Complete Edition
For offline installs, Rockstar still provides a Manual Activation Guide where you can input your serial and "Unlock Request Code" to generate an activation. Summary Table: GTA IV Versions DRM System Activation Method Retail (2008) SecuRom / GFWL Manual Serial Key (Manual) Steam (Pre-2020) GFWL / SecuRom Steam CD Key Complete Edition (2020+) Rockstar Launcher Tied to Social Club Account Grand Theft Auto Iv License Key.txt
The good news is that playing GTA IV in the 2020s is easier than ever, and it doesn't require hunting for shady text files. In 2020, Rockstar Games replaced the original version