Virus messed up my registry not completely su

Hello,
i got a virus and right away i tried to remove it by going into task manager and removing the program that kept starting up which was called chn.exe, the way this thing worked is that everytime i tried to open firefox it would say i wasnt protected and bring up this fake security alert, removing it was my last resort because the virus denied access to the internet. now since i removed that file im having problems with opening or running anything, it keeps saying that it doesnt recognize how to open .exe files and it doesnt allow me to install or download anything because of errors i cant run regedit.exe or regedit.com none of them work, my programs already installed work once i try to open a file that pertains to it. it is really confusing and i probably really messed up my computer please help i cant find answers anywhere.