Last time I touched on file extensions, so I'll elaborate a little more since understanding file extensions and file types gives you a big head start toward getting a handle on what's stored on your computer. The three-letter file extension on the end of most files (such as .doc, .exe, .psd, and so on) indicates what type of file it is. Windows uses those three letters at the end of a file to figure out what software program to run when you double-click on the file. For example, on most systems, if you double-click a file called resume.doc, Microsoft Word opens and runs your file. If you don't have Word on your system, Word Pad opens instead. So, in Windows parlance, Word is associated with the .doc extension. Frequently the extension stands for something, so they're easier to remember. For example, .doc stands for document, .bmp stands for bitmap, and .ico stands for icon.
These file associations are set up when you install software. However, sometimes the software can make associations you don't necessarily want. For example, after I loaded a graphics application, it decided that every graphics format should be associated with it. I disagreed and I decided to switch some of the associations.
Here's how you change a file association. Go to Windows Explorer and choose View|Folder Options. Click the File Types tab. Scroll down the Registered File Types list until you find the file type you are looking for. Click the Edit button and then click the Browse button. Find the folder that has the program you want to use to run this particular file type. (Remember that the program file will end in .exe.) Double click the filename and it appears in the Application Used To Perform Action box. Click OK.
Now the next time you double-click a file with that extension, the program you selected will run it. Proving once again that yes, sometimes you can outsmart software. (Or at least until some wayward installation program automatically steals the association back again.)