>Fossil probably does not understand %SystemRoot%\system32, which is what's on PATH for that folder.

I think you've hit on the problem here. It works perfectly well on XP though, which is why I'm puzzled. I will try your suggestion but ultimately will end up with Fossil back in system32, where (IMO) it belongs.

>This is not a problem of fossil.

I believe it is. Please see below for my reasons.

>The mentioned error message is a MS Windows message, documenting, that the requested command is not found in the path.<br>
><br>
>So you should check:<br>
><br>
>is the path really correct<br>
>how do you call fossil, MS Windows doesn't use the path variables in all call variants<br>

Looks like you didn't read my ticket. I'll explain again:

At the command prompt, I'm running "fossil ui". ("fossil server" does the exact same thing.) There is a known good, open fossil in the working directory. Fossil opens a web browser (Firefox in this case) and gives it the path "localhost:8080" as expected.

The problem occurs when Firefox accesses localhost:8080. Fossil is definitely listening on 8080/tcp because it reacts to connections on localhost:8080. The way it reacts is to output this error on stdout:

'"fossil"' is not recognized as an internal or external command, operable program or batch file.

instead of returning a web page to the browser.

You're right that this error is generated by the OS, but I believe the flaw is in Fossil. IMO Arnel's suggestion is correct, that Fossil is not interpreting %SystemRoot%\system32 properly. I will now attempt to prove it.