For whatever reason, the 64-bit Windows Installer doesn't seem to register the .7z file extension with the 7-Zip GUI (or with anything, as far as I can tell).
How do I go about doing it. A simple "open with"(7zG.exe) doesn't work, because 7-Zip apparently requires a command-line that doesn't fit the usual pattern for the shell invoking programs. I can't seem to divine what this syntax might be from the command line (/? -? --help all give 'invalid syntax' errors).
How do I set it up so that clicking on a .7z file opens the GUI?