Issue: The Internet Explorer Accelerator feature takes some user selected content and using the accelerator XML definition, constructs a URI that Internet Explorer will navigate to, or optionally display in a preview window. Like following normal links in the browser there's no way to have that link open in a different browser.
Workaround: Create an Internet Explorer plugin to open the current page in the user's default browser. Your users can use this plugin to open whatever page they like in their default browser.