KSP trying to re-install instead of open?

[Galathor]

Last night my game crashed on a loading screen and when i went to boot it up today a strange thing  happened- instead of starting up I got the Steam window showing me how much free space my computer has and asking if I wanted to install KSP. I tried going into the program files and opening from the launcher, which worked but when the game opened all of the menu options text had changed to a bunch of alphanumeric gibberish. When I bring up my Steam library and select KSP the button says 'INSTALL' instead of  'PLAY' even though it still shows my hundreds of hours played.

[jimmymcgoochie]

Sounds like a corrupted Steam install. Try verifying the game files (right click KSP in your Steam library > Properties > Local files > Verify integrity of local files) and if that doesn't fix it, uninstall and reinstall KSP- remember to copy your saves from KSP/saves/your_save_name(s) to somewhere else e.g. desktop so they don't also get deleted.