MIME types, also known as media types, identify files opened in Web browsers and email clients, helping programs such as Internet Explorer decide how to display each file. If a MIME type indicates an HTML file -- a website -- Internet Explorer displays it directly. Other types of files open using other programs on your computer. Unlike some Web browsers including Firefox, Internet Explorer consults the Windows registry to select a program to use. To change these settings without editing the registry by hand, use the Default Programs Control Panel.
Search for "Default Programs" on the Start screen and open the Control Panel from the search results. Alternatively, press "Windows-X," click "Control Panel," set the view to "Large Icons" and click "Default Programs."
Click "Set Default Programs" to set specific programs to open specific types of files.
Pick a program and press "Set This Program as Default." For example, if you want both DOCX and RTF text documents to open in Wordpad, select Wordpad and set it as the default. Alternatively, press "Choose Defaults for This Program" and pick individual file types for it to open.
Press "OK" after setting up as many programs as you want.
Click "Associate a File Type or Protocol With a Program" if you need to specify programs to load other file types not found in the by-program list.
Select a specific file extension and choose "Change Program." Pick a program from the list. If you don't see the program you want to use, click "More Options." If your program still doesn't show up, choose "Look for Another App On This PC" and locate it manually.
Press "Close" when finished. Your changes will affect all future files opened in Internet Explorer.
No matter which programs you set as the default for TXT (plain text) and HTML (Web page) files, opening these media types while browsing in Internet Explorer displays them directly in the browser window.
To change your default Web browser, open the "Set Program Access and Computer Defaults" section in the Control Panel. Choose "Custom," open the drop-down menu and pick the browser you want to use from the list. This modification affects Web links opened from other programs, but sites visited directly in a non-default browser will still load in that browser.
If you need to find MIME types in the registry manually, run the Registry Editor -- Windows stores the types at HKEY_CLASSES_ROOT\MIME\Database\Content Type, with the file extensions for each type listed in keys labeled "Extension." Altering the registry by hand can cause system errors; most people will never need to make these manual edits.
Information in this article applies to Windows 8 and 8.1. Procedures may vary with other versions.