If the program you are talking about windows photo viewer, this should help.
1. Copy the code from this post over at TenForums into Notepad and save it as a REG file (call it whatever you like, maybe photoviewer.reg).
2. Double-click on your new REG file to merge it with your Windows Registry. You will need to click through the User Account Control and a few other windows to allow the file to make changes to the Registry.
3. You should now be able to see the Windows Photo Viewer and set it as the default program for various image files. To do this, open the Control Panel and go to Default Programs > Set Default Programs. Find Windows Photo Viewer in the list of programs, click it, and choose Set this program as default. This will set the Windows Photo Viewer as the default program for all file types it can open by default.
If the program you are referring to is different, step 3 alone could help
Hello Susan, thank's for the extra info. I found this info on their website:
Open Paint Shop™ Pro® and select File | Preferences | File Format Associations. In the File Format Associations dialog box, select the file types you would like associated with Paint Shop™ Pro® and click Ok. Test the file association by double-clicking a file.
The following Windows procedure can be used if the previous failed to associate the file type.
1. Right click on a file that is of the file type you would like to be associated with Paint Shop™ Pro®, e.g. mypicture.jpg
2. Select Open with | Choose program.
3. Select Paint Shop Pro from the list of available programs by clicking it once.
4. Click the box at the bottom that says, "Always use this program to open these files" - (only available in Windows XP)
5. Click OK.
This will associate all files of this type with Paint Shop™ Pro®. You will need to repeat this procedure for each type of file you would like to associate.