Hmm, mailto definitely should not be missing.

Sometimes the file which stores those application handler/download actions becomes corrupted. Since it is difficult to edit, when there is a problem, we generally suggest renaming the file and allowing Firefox to rebuild it from the Windows registry. That may not help if mailto is missing from the registry, but I think it's worth a try:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename mimeTypes.rdf to mimeTypes.old (or another name of your choosing, in case you decide to roll back this experiment).

Start Firefox back up again and return to the Options page to specify your preference. Is mailto listed once again?

Thanks for the advice - worked like a charm!!! The windows live program entry came in automatically.