Win Open With

To open a document using a different program than the one currently associated with it (see Win File association), right click on the file on the desktop or in Explorer and select Open With. Then, choose the program you want to use. If the program is not in the list, select Choose Program and select one from Other Programs. If the program still cannot be found, you can select Browse and go to the executable file of the program you want to use. However, you will have to know the name of the file (.EXE file) and its exact location (path) on the hard disk.

Windows May Ask You As Well
If you click a document to open it that has not been previously associated, you will get a dialog box that says "Windows cannot open this file." As mentioned above, you can select the program by name or by its executable file if you know it. You can also let Windows use the Web service to find the appropriate program, but chances are that it may not find anything.