[Game Root Folder]\Hitman Absolution\
Rename the original steam_api.dll to steam_api.dll.backup . This allows you to restore the original file if the new one causes the game to crash.
(If downloading from a random DLL site) Effectiveness: 9/10 (If the file matches the game version)
Do not download a DLL from a website. Instead:
Ten minutes later, Elias clicked Play in Steam. The game launched perfectly. He even got the Professional Edition extras—the sniper challenge, the art book PDF—all working.
The file is a critical component for Hitman: Absolution Professional Edition