NirSoft develops nifty, compact, free utilities for a broad range of specific uses. Its URLProtocolView is an easy-to-use tool that displays all URL protocols currently installed in your system, such as ftp, telnet, and mailto. It displays each protocol's name as well as a description, the command line that is executed when you click or type the URL, the name of the product in which it originates, and the company that developed or published the software. You can also use it to easily enable or disable each protocol. (Please don't disable mailto, though!)
URLProtocolView downloads as a compressed file but can be used immediately after extraction with no further installation or other software or files required. That, plus its compact size and freeware license, gives it a portability that will win the gratitude of many system administrators. At 38.23K, it's old-school small, and it fits on just about any storage device. Despite its compact size, it has a full-featured Windows-style interface, including File, Edit, View, and Help menus, which are always needed but too often overlooked in free software, as well as colorful icons and other nice touches that bolster the efficient feel. The efficiency extends to the program's operation, as it quickly finds and lists all protocols installed on the host machine.
URLProtocolView is freeware that can be copied and distributed but not modified. New releases add support for x64 systems such as Windows Vista as well as a command line option for sorting.