It's a combination of a broken Apache and probably some confusion about the scripts since the upgrade put them in a different place (there should have been a note about that in the install, sorry). There's no chance you're using a unix version on NT. It wouldn't even begin to install. 4.0.5 will not work under Apache for Windows without modification (Apache for Unix is not a problem).
Uninstall all messed up versions.
Verify by hand that all related scripts are gone from all directories.
Install the latest downloaded version.
Download the dowalk 4.1 from the website and replace the one just installed (make sure there's no extension).
Go to the admin interface and login.
If the exec does not work please indicate what is printed for the version info at the top-right of the admin page as well as the last 4 lines of the dowalk file itself.
Uninstall all messed up versions.
Verify by hand that all related scripts are gone from all directories.
Install the latest downloaded version.
Download the dowalk 4.1 from the website and replace the one just installed (make sure there's no extension).
Go to the admin interface and login.
If the exec does not work please indicate what is printed for the version info at the top-right of the admin page as well as the last 4 lines of the dowalk file itself.