Virus problem. Can't open up .exe's without designating the .exe I'm trying to open in Browse?

Today, I got a strange virus. After looking through a site, Adobe Reader pops up on its own and then my AVG finds a virus. I've had a virus enter through Adobe Reader before, and I wonder how the heck it does that, but that's not what I'm asking.

After the main parts of the virus were removed, I tried opening up FireFox only to find a message saying:

Open With

Choose the program you want to use to open the file:

File: firefox.exe

Then it shows a list of programs.

Now, this has happened to me before but I don't know how to fix it. And this happens to every single one of my applications and .exe files. Also, after I designate FireFox to open, it shows another box saying that it can't find a strangely named file... But it works after I press OK.

Anyone else have this problem before? Any known fixes? Suggestions? Any and all help will be greatly appreciated.