I have downloaded the OSGeo Installer (on Windows 7 x64) and run it, selecting the Desktop Express Install option. All of the files were downloaded and the installer reported a successful install, however whilst I could find the downloaded files, I could not find the installed instance. An OSGeo4W directory was created but contained only a few MB of files. I have tried to rerun the installer and it only confirmed that the previous installation was successful and that no files needed downloading. All the downloaded files were still in tarballs so it appears that the installation process after downloading had not taken place. QGIS has previously been on my system but all previous and development versions were uninstalled using the provided uninstallers.
How to I bring about an installation process that installs desktop QGIS using the files downloaded by the OSGeo Installer?