If you are still having problems installing iTunes on Windows, then try the following:
I suggest you download and install the Windows Installer Cleanup Utility from here.
You can use the utility to remove installation information for programs that were installed by using Windows Installer. Be aware that Windows Installer CleanUp Utility will not remove the actual program from your computer. However, it will remove the installation
files so that you can start the installation, upgrade, or uninstall over.
Once you have opened the Windows Installer Cleanup Utility, it will populate all of the programs installed on your computer by Windows Installer. Select iTunes and then click on the Remove button. It will remove any corrupt or incomplete iTunes files from
your computer. Then remove Bonjour and QuickTime. They will both be installed again with iTunes.
NOTE: iTunes Store purchases or songs imported from CDs are saved in your My Music folder by default and are not deleted by removing iTunes.