Restore file extensions

I have a user who has a bunch of different file types all opening in Word after he ran his spyware remover. I always thought there was an easy way to restore file extensions back to system default, but I can't seem to find it. Any ideas? (Even his email is trying to open in Word)

 

To change a file extension, please do the following:

1. Right-click a file who's program association you want to change
2. Select 'Open With'
3. Select 'Choose Program'
4. Select the program you wish to use if it is listed, if not, click 'Browse' and navigate to the program's main executable.
5. Ensure that the checkbox next to 'Always Use The Selected Program To Open This Kind Of File'
6. Press 'OK'

Windows will now associate the filetype with the program you selected, and open it with that by default.