Ok, I've exhausted all the ideas in related QtCentre qwt install threads, and read all the qwt product 'install' notes, but I can not successfully install Qwt into my QtCreator environment.

System:
Windows XP Pro with SP3 + all current updates
VS6 (shouldn't matter... just listing for completeness)

Steps to repro:
1) Download either:
qt-sdk-win-opensource-2009.01.1.exe
qt-sdk-win-opensource-2009.02.exe

2) Execute, using all install 'defaults' (Installs Qt to C:\Qt\2009.01\...)
3) Download Qwt (qwt-5.2.0.zip) and unzip to C:\qwt-5.2.0 (INSTALLBASE folder specified in qwtconfig.pri)
4) Edit qwtconfig.pri : change to build all:
CONFIG += debug_and_release
CONFIG += build_all
(and comment the CONFIG += release statement)
(also uncomment CONFIG += QwtExamples )
5) Open Qt command prompt and execute the following:
Cd C:\qwt-5.2.0
qmake qwt.pro
make
make install

Result:
Qwt is successfully compiled and linked, including the examples
The examples execute without any problems from the Qt command prompt
The following files are copied to C:\Qt\2009.02\qt\plugins\designer
qwt_designer_plugin5.dll
qwt_designer_plugind5.dll

But..
Open QtCreator
NO Qwt listing in the “Help | About Plugins…” list
After creating a new Qt GUI application (foo) in QtCreator, go to the QtDesigner (foo.ui) – there are NO qwt Layout items.

Alternative measures tried (one at a time)
1) Both the Qt SDK 4.5 releases, 2009.01 and 2009.02 using the install/build/install steps outlined above

Or…
2) Additionally copy the following files to C:\Qt\2009.02\qt\plugins\designer
libqwt_designer_plugin5.a
libqwt_designer_plugind5.a

Or…
3) Alternatively, completely build Qt, QtDesigner, and qwt, specifically using a “make release”. Even after the appropriate “make install” commands, (also in the Qt SDK releases with binaries included) THE sizes and build dates for many dll’s are NOT the same in the QtRoot\bin (and subfolders) vs. the QtRoot\qt\bin folders. (Or QtDesigner build folders) All updated files were manually copied to the QtRoot\bin folders.

Result: YESSSS… qwt items are listed in QtDesigner ! I successfully added a qwtPlot to a form and saved the file. At this point, selecting ‘Build’ makes Qt crash! But going to the Qt command line and building with qmake / make, creates an EXE that successfully displays the qwtPlot. (path and include information is correct)

So… TWO related questions:

1) How can I successfully install qwt extensions to Qt?
2) Why are the dll’s so different (date and size) between the Qt\bin and Qt\qt\bin folders?