From NirSoft Freeware:
URLProtocolView is a simple utility that displays all URL protocols (for example: ftp:, telnet:, mailto:) that are currently installed on your system. For each URL protocol, the following information is displayed: The protocol name, the protocol description, the command-line that is executed when you type or click the URL, the product name, and the company name. This utility also allows you to easily enable/disable the URL protocols.
What's new in this version:
Version 1.15 added support for x64 systems, and sorting support from command-line.