Prototype 2 — Pc English Language Pack

Cause: The audio pack was not installed correctly. Solution: Go to Prototype 2\audio\speech\. Delete or move the non-English voice folder (e.g., ru_speech). Copy the en_speech folder from the language pack. The game defaults to English if the designated folder exists.

You might ask: Is it worth hunting down a language pack for a game over a decade old? Prototype 2 Pc English Language Pack

Absolutely.

If you are playing a version that required a "fix" or crack applied manually to run, the language setting is almost certainly inside a .ini file in the game directory. Cause: The audio pack was not installed correctly