The problem is that you're running on a Microsoft IIs server and this code is for Apache-based servers. While there are ways to use .htaccess on Microsoft IIs servers, I doubt GoDaddy supports such a solution on shared hosting accounts. You might request GoDaddy change their servers to support these file types directly, but I wouldn't expect them to agree.
There might be a way to add some ASP code to your pages to handle this automatically like .htaccess does on Apache servers, but the only solution I can think of would be to write a PHP script that would fetch the media file, send the correct MIME type header for you, and then echo the file contents. Then you'd set your HTML <video> tags to point to this script with a query string that would include the actual file name. It would be a kludge, but it would probably work. Sorry I can't be of more help. Good luck!
I figured it out finally. I had to set up a linux based hosting account, then upload the .htaccess file with the mime types. It works! I guess windows hosting account won't work with the HTML5 video tag. Thanks for your help, you put me in the right direction.
It's not that the tag won't work with a IIs server, it's just that the server has to be properly configured to use the proper MIME-type headers for these particular kinds of video files. But I'm glad you got it sorted. Good luck!