Left 4 Dead apparently uses the .sav file extension, not sure if this is going to cause any problems, it hasn't so far. Just letting everyone know. After installing left 4 dead all my .sav files got the the L4D icon
There shouldn't be any problems. And .sav is just the common extension people on BYOND use for saving data - you could have the extension as any way you want, ex: .dmv
Half Life 2 engine uses .sav extension, so it registered it. Just don't double click BYOND savefiles, or else L4D might try loading them. After uninstalling L4D icons should disapper, so nothing to worry about
Seems pretty dumb of the game to register .sav, since that file extension has been widely used by games of all kinds since DOS crawled out of the primordial ooze. You might want to just unregister that file type, because no program should go around thinking it owns that.

I have a similar issue with LDraw and related programs which use .dat as an extension, apparently owing to a complete lack of thought on the author's part.

Lummox JR