Hello.
Sorry for this boring question but I can not find a solution and then here I am

I am working on a Windows XP platform (but I have the same problem on Linux)
I downloaded and installed QT-SDK LGPL from : http://qt.nokia.com/downloads/downloads#lgpl
I downloaded qwt-5.2.1 from : http://sourceforge.net/projects/qwt/

I compiled qwt with VisualC2008 , because qtsdk requires that the plugin is compiled as well (otherwise not working) .

I copied the qwt5_designer_plugin.dll in :
C:\Qt\2010.02.1\bin\designer
C:\Qt\2010.02.1\qt\plugins\designer
C:\Qt\2010.02.1\qt\bin

I copied the qwt5.dll in :
C:\Qt\2010.02.1\qt\bin

I added these paths to the system :
C:\qwt-5.2.1\lib;C:\qwt-5.2.1\src

And this is my pro file :
#-------------------------------------------------
#
# Project created by QtCreator 2010-05-06T09:44:36
#
#-------------------------------------------------

TARGET = QTW_TEST
TEMPLATE = app


SOURCES += main.cpp\
mainwindow.cpp

HEADERS += mainwindow.h

FORMS += mainwindow.ui

INCLUDEPATH += C:\qwt-5.2.1\src
DEFINES += QWT_DLL
LIBS += C:\qwt-5.2.1\lib\qwt5.dll
The result is that in the palette I see the qwt components and can also add them to a form but when I try to compile I get this errors:

release/mainwindow.o:mainwindow.cpp.text$_ZN13Ui_MainWindow7setupUiEP11QMainWindow[Ui_MainWindow::setupUi:-1: error: undefined reference to `QwtPlot::QwtPlot(QWidget*)'

:-1: error: collect2: ld returned 1 exit status
How can I resolve and, above all , how can I install the qwt libs in a clean mode ?
Is there a step by step tutorial for a monkey?

Thanks to all