You install a program. You decide you don’t like it. You uninstall it. But it changed your associations for a whole group of files, and now your original program doesn’t work. What do you do?
Visit Doug Knox’s site and pick one of these handy-dandy downloadable Windows XP File Assocation Fixes. He’s got 24 in all, from Batch Files to Zip Folders.
This also comes in handy if you inadvertently make a wrong choice when using the File Types tab on the Folder Options dialog box.
Ed Bott 
About time! The worst offenders are usually archive and imaging apps. The most aggravating thing is that when you tell Windows to associate and it doesn’t stick. Then it’s registry-hack time.