Well, I've just run the March 2010 version on three different computers -- two x86, one x64 -- and it works on all three. I can't make it fail!
There are three successive lines that can trigger that error message. Here are versions that you can try at the command prompt. If you can get one of them to fail, that might give us a clue what's going on.
if not 1 == 01 echo FAIL (looks like CMD.EXE)
*if %@index[4NT!TCC!TCCLE!TCMD32!,%_cmdproc!] == -1 echo FAIL (unknown shell)
*if %_4ver lt 7 echo FAIL (_4VER less than 7)
Do you set "hkcr:\directory\background\shell\(text)\command".
What this does is allow to write click on a background of an open folder, and run the command in there. Here is a sample regedit for my background setting. Also there's a '4nt here' dll, which i suppose could be modified to show tcchere.dll, which does this.
I have a version of http://code.kliu.org/cmdopen/ this, which does a lot of the nifty stuff for cmd.exe, but you can patch the dll to use 4nt.exe or tcc.exe or something else. What i am really looking for is something that will run under cmd.exe, use apppath, and load the proggie named. Something like write.exe, but without leaving the console. You could remove a lot of stuff from the path, and still run exefiles.
I have a modified version of 4nt.exe = hacked write.exe -> 4ntu.exe -> apppath -> l:\newin\jpsoft\4nt.exe, but running 4nt.exe starts a new window, rather than load it in the current window. [putting 4nt in place of 4ntu.exe is circular. You got to use some bogus name.]
The cmdopen thing has been taught to run cmx.exe, which is one of several versions of write.exe, designed to run 4nt or tcmd or tcc (which does not run in my windows, but one day i will upgrade to XP, i fear).