HOWTO: Revert your Windows XP Picture Viewing Preferences

Open a folder on your computer containing pictures.

Right click on one of the pictures, select Open With... and then select Choose Program...

In the subsequent window that opens, select Windows Picture and Fax Viewer from the available choices at the top, and make absolutely sure that the check box at the bottom labeled Always use the selected program to open this kind of file. and then click on OK.

You may discover, as you work with pictures, that some will open with the Default picture viewer, and some might open with whatever program you had wanted to get away from in the first place. The reason for this is due to the fact that there are several different "types" of pictures that Windows recognizes. The procedure above only reset the type of picture that you happened to select at the time. The solution is, as you discover a picture "type" that has been "hijacked" to simply follow the above procedure on that specific picture. That will then subsequently reset all pictures of that "type"