If the wrong program is opening your file (for example Windows Explorer opens all .gif files and you want Paint Shop Pro to open them) then you need to change how the .gif files are registered. Once changed, all the files with that extention will now open with the new program you have selected)
Open MY COMPUTER or MY DOCUMENTS.
Now return to File Types Page and you can see that the file will now open with the program you selected. You will notice that you can also change the icon associated with that file type, plus other actions for the file.
For more information, or if you still have questions, give us a call at (540) 776-1122
If you only want the new program to open a particular file once and go back to the original...