The great Vanishing Act of INetMgr.exe on my Windows 7 x64 system

That's an interesting one. Try launching your command prompt with elevated privileges in case UAC is fighting with you. My only other guess is that %windir% is set differently in your path for the command prompt somehow. Try navigating to it with the explicit path. Also, try creating a test file like 'test.txt' from your command prompt and make sure that it shows up in Windows Explorer, to make sure that the paths between the two apps aren't messing with you.

FWIW - I was seeing exactly the same problem on my Windows 2008 R2 "desktop". I never did find a fix or an explination.

But a workaround for me was to copy C:\Windows\System32\inetsrv\InetMgr.exe to a new folder (e.g. "E:\Apps\IIS\InetMgr.exe"). Now I can execute it from a command line in this location, UAC comes up, and all works fine from there on.