On my Computer I go to "My Computer", then I pick "Tools" from the drop down menus, then folder options. Then I pick the "File Types" tab. Then in the box there just find the file type you need to set back, pick it, and then use the button which changes which program the file type is associated with.

I'm running win2k so it may be a little bit different, but it's generally the same procedure.

A+ Certified PC Tech Guy/Seitentaisei