If you double-click on a data file in Windows Explorer (eg a picture file or document), then Windows will open the program that it thinks “controls” that type of file, and then open the data file (document) in the newly opened program.
Sometimes, you may prefer a different program to open a particular type of file. For instance, the Windows Picture and Fax Viewer may open “jpg” files whereas you would like these to be opened with Photoshop.
To change the program that opens files (known in Windows terms as changing the file association) take the following steps (these instructions are for Windows XP):
1) In Windows Explorer, open any folder
2) Click on “Tools” in the top menu
3) Click on “Folder Options”
4) Click on the “File Types” tab
5) Scroll down the list to find the type of file you wish to change (for instance, JPG, JPEG, and JPE are all picture files that could be produced by a digital camera)
6) Click on the file type you wish to change
7) Click the “Change” button. This will produce a list of the programs that Windows suggests may be suitable to open this type of file.
8) If you see the program you want, double-click on it and then close any open boxes.
9) If you don’t see the program you want, you can browse for it by clicking on the “Browse” button. You will then need to identify the program you want, double-click on it and then close any open boxes.
In this example there are 3 different file names associated with jpg files (see (5) above), so repeat the exercise for all three types if you want Photoshop to open any type of jpg file.