Each game is a little different, but you basically jus. Installed again (to the right HDD) and now its discovering existing files. How to Install Left 4 Dead 2 Mods via SteamInstalling mods for Left 4 Dead 2 on Steam is super simple. Install L4D2 (now has directory option), cancelled that and renamed the folder back to the original name. Uninstall L4D2 (renamed folder) and authoring tools. Although they were installed on the game hard drive, I don't know why it would cause the game to install somewhere else. Halfway through typing this comment I think I figured out what was causing it. I'm trying to mess with the libraries but I'm not getting a prompt to select install directory. The only library I have in download settings is F:/steam. I've tried copying the install it makes on E over to F and try running it from steam, but it redownloads it (and running it from explorer gives the -insecure error).

I get what you're saying with discovering the libraries, but steam is installed on F along with all the other games.

How to install left 4 dead 2 on steam