If you are trying to rebuild the SDK you might get errors because of the previous build (SDK is already build with MingW)
I suggest you download the source (4.7.1) from "here":http://get.qt.nokia.com/qt/source/qt-everywhere-opensource-src-4.7.1.zip or older source can be found "here":ftp://ftp.trolltech.com/qt/source/
And then, after you unzip the archive, you do this (from the VS command prompt navigate to the unzipped Qt folder):
configure.exe (with desired parameters)
nmake (it will build everyting including examples and demos...)
or alternate...
nmake sub-src (build the framework)
then
nmake sub-tools (build the tools: Designer...)
install the VS add-in