With that one, let's try the following procedure.
First, head into your Add/Remove programs and uninstall your QuickTime. If it goes, good. If it doesn't, we'll just attend to it when we attend to iTunes.
Next, download and install the Windows Installer CleanUp utility:
Description of the Windows Installer CleanUp Utility
Now launch Windows Installer CleanUp ("Start > All Programs > Windows Install Clean Up"), find any iTunes and/or QuickTime entries in the list of programs in CleanUp, select those entries, and click “remove”.
Next, we'll manually remove any leftover iTunes or QuickTime program files:
(1) Open Local Disk (C:) in Computer or whichever disk programs are installed on.
(2) Open the Program Files folder.
(3) Right-click the iTunes folder and select Delete and choose Yes when asked to confirm the deletion.
(4) Right-click the QuickTime folder and select Delete and choose Yes when asked to confirm the deletion. (Note: This folder may have already been deleted if QuickTime was successfully removed using Add/Remove Programs earlier.)
(5) Delete the QuickTime and QuicktimeVR files located in the C:\Windows\system32\ folder. Click Continue if Windows needs confirmation or permission to continue. (Note: These files may have already been deleted if QuickTime was successfully removed using Add/Remove Programs earlier.)
(6) Right-click on the Recycle Bin and on the shortcut menu, click Empty Recycle Bin.
(7) Restart your computer.
Now try another iTunes install. Does it go through properly now?
