Windows Vista might not assign HTM or HTML file extension to Microsoft Internet Explorer (IE), but Vista will launch Internet Explorer when we click on the HTML pages.

If the computer doesn't assign HTM file extension to the Internet Explorer and the application want to open a HTML page by file extension, then the application cannot find the associated default program and cannot open that HTML page.

   Setup HTM file extension associating with Internet Explorer   

1. Go to the Control Panel, then click on Default Programs icon.
   
    
2. If you want to Check HTM is associating with Internet Explorer or not first, then click on Associate a file type or protocol with a program.
   
    
3. Scroll down the Current Default List, to find .htm and .html.
   
   Then click Close button go to back the previous screen
    
4. if you cannot find .htm name in the Current Default List and you want to add the file type extension to a default program, then click Set your default program.
   
    
5. Then look for Internet Explorer program, highlight it, click Set this program as default to assign file extension htm and html to Internet Explorer.
   
    

Setup HTM file extension associating with Internet Explorer for Windows XP computer

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