I can't seem to install the Source mod Fortress Forever.
My understanding is that I need one of the games on this list. However, I have both Portal and Half-Life 2: Deathmatch from that list.
Why can't I install the game?
Fortress Forever requires a Steam account with Source SDK Base 2006 available.
Source games that Valve has given away for free do not include the Source SDK, Source SDK Base 2006, or Source SDK Base 2007 packages. This includes Half-Life 2: Deathmatch and Half-Life 2: Lost Coast when gotten through the ATI or nVidia free game offers, and Portal when it was free in May 2010 when the Mac version of Steam launched.