[Late response, but posting for others who may also have hit this particular error].
Regarding the error:
‘...\configure.exe’ is not recognized as an internal or external command...
I was getting this error as well. Digging into it a bit, in qtbase\configure.bat, there is a test for the existance of a file called '.gitignore'. If this file does not exist, then it jumps to the end of the script and attempts to run 'configure.exe'. If the file does exist, then it first builds configure.exe (among other things).
I suspect you're getting this error because, like me, you downloaded the sources from the link on http://qt-project.org/downloads rather than getting them via git. For some reason, the .gitignore file is missing from the qtbase directory. When I got the sources via git, the file was present.
Just create the file (e.g. "echo foo > qtbase.gitignore") and you should be able to run the configure script successfully.
[Perhaps the configure.bat script should instead test for the presence of qtbase\configure.exe, rather than qtbase.gitignore?]