Need help urgent!!

hey i was playing garrys mod for one day, the next day i for some reason tried to open a map file in half life 2 exe, i realise now is really stupid and i have no idea why i even tried this. but the real problem is that i run garrys mod, click on my last save, then it crashes i suspect this is because me trying to open the maps in hl2 set them to it, now i cant change them back by right clicking, open with, then unchecking use this program every time. they need to be an unknown file. but i cant change them or reset them at all. please post. any comment is appreciated.
i have tried to load up all of the maps and all of the saves but it still crashes.
the file is called BSP.
and yes this is garrys mod 9.

EDIT* i also found two LST files attemting to run through hl2, if someone gives a way to fix my problem i will try my first problem, if that doesnt work i will try to fix my new found files.

Get Bought Garrysmod.

Thats why we play Garry’s Mod 10 because he updates it.

Yeah.

All answers to GMod 9 questions is:

Get GMod 10.

GMod 9 is also unsupported here.