Media Converter is a fast free conversion utility that works in your browser window. While you can create an account, it will also work on-the-spot without needing any kind os sing in or email account. Simply upload the file, or give a URL, specify the output format and after a few minutes of chugging away, you get a link for your new file. (The free version has limits: You can only convert 5 files per day. Free users cannot convert files larger than 100MB.)
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