You have several options here. You can install the version provided by ubuntu:
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sudo apt-get install qt4-qmake
@
The version depends on Ubuntu you are using, however.
Or you can download the prebuild package from Qt Project "archive":http://download.qt-project.org/archive/qt/4.7/.
Or you can download the source code and compile Qt yourself.
I strongly suggest upgrading to newest Qt 4 version: it's fully source and binary compatible, and you get numerous bug fixes, performance improvements, new features etc. for free.