Missing .exe file association in Windows XP

I recently encountered an XP machine that seemed unable to execute anything. When opening an executable I'd be met with either "Application Not Found" or else the Open With... dialog box. Obviously this made the computer pretty well unusable. Though I'm not entirely certain how this occurred (virus?) I was able to correct the missing file association which enabled me to run the virus scanner. This page has a number of .reg files with the correct XP file associations for lots of different formats, notably .exe. There's some instructions at the top for getting these keys imported to the registry without being able to run regedit, but I found explorer correctly handled the .reg file without any tinkering. Once those keys were in place everything worked as it should. Easy as pi!