How to Specify Which Application Opens Which File Type
Setting the default application that opens when you click on a file is relatively easy in Windows.
The process is nearly identical in Windows 7, Windows Vista and Windows XP.
Simple right click on the file and select ”Properties” in the popup.
In the “Properties” window, on the “General” tab, you will see “Opens With:” and the current application.
Next to the “Opens With:” information you will see a “Change…” button. Click that.
In the “Opens With” window (that pops up when you click “Change..”) you will see the current applications that Windows recognizes may be compatible with opening the file type you have chosen.
You can either select the application from the icons or click the “Browse…” button to locate the .exe file of the application you wish to assign. Then, after making sure that “Always use the selected program” is checked, click “Okay” and you’re done!

Microsoft provides some additional information for Windows XP, Windows Vista, and Windows 7.
It’s as easy as that!
PS: I use this to specify which documents I want Windows to open regularly vs which ones should be handled by GDocOpen. Similarly, I assign my graphics file PSD’s to Photoshop but my jpg/png’s to Paint.net.

