Make Documents and Media Open in the Right App

MY WIFE’S PC came with a trial of Microsoft Office 2007, but I installed IBM Lotus Symphony on the system instead—in part because it’s free, and in part because I think it’s easier to use. But when the missus attempts to open certain file types (such as .docx or .rtf), up pops Office 2007, its trial period having long since expired. Why don’t these files open in Symphony?

For whatever reason, certain file types remain associated with Office, so
Windows doesn’t know that it’s supposed to direct them to Symphony. Fortunately, the problem is easy to fix. In Vista and Windows 7, click Start, type Default, and press to load the Default Programs menu in Windows. Then click Associate a file type or protocol with a program, choose the file type in question, click Change Program, and go from there. That’s a lengthy process. I prefer to right-click any file that’s incorrectly associated (such as one of the aforementioned .rtf files), mouse over Open With, and click Choose Default Program. If the program you want appears under Recommended Programs (and it should), click it, and make sure the checkbox for Always use the selected program to open this kind of file is checked. Click OK and you’re done.
Henceforth, any attempt to open that file type (not just that file) will cause Windows to load the selected program. If the program doesn’t appear, click Browse to locate its executable on your hard drive. That’s not the easiest task in the world, but you’ll need to do it if you want to re-associate that file type. The most common file association hassle you’re likely to encounter involves media files—MP3s, videos, and the like—that refuse to open where you want them to. This solution works with those kinds of files as well as with document files.

Source of Information : PC World December 2009