Project ERROR: Unknown module(s) in QT: core

[Pikko]

Hello,

I'm trying to follow the following instruction:
http://qt-project.org/wiki/QtVSAddin#e6884aa92ce8319781c2b2b6d626dc08
for Windows but I get a problem in this line:
@cd ..\tools\qmakefilereader
qmake@

Whenever I call qmake I get this error:
Project ERROR: Unknown module(s) in QT: core
I google this problem but don't seem to find a solution. qmake -v shows me the correct path to the libs. I never moved my Qt-installation or did something similar.
Where is the problem? I really don't have any idea.

Thanks for helping :)