The older version of Apple Mobile Device Support Cannot be removed. Contact your technical support group.
Download the Windows Installer CleanUp utility from the following page (use one of the links under the
thingy on the Major Geeks page):
http://majorgeeks.com/download.php?det=4459
To install the utility, doubleclick the msicuu2.exe file you downloaded.
Now run the utility ("Start > All Programs > Windows Install Clean Up"). In the list of programs that appears in CleanUp, select any Apple Mobile Device Support entries and click "Remove", as per the following screenshot:

Quit out of CleanUp, restart the PC and try another iTunes install. Does it go through properly this time?