Hello. I was having this issue also with an iTunes installation on Windows 10 - 64 bit.
(It was being caused by a problem with Apple Software Update not being able to be Uninstalled, Changed, OR Repaired. I deleted items from the registry regarding iTunes6464.msi, did 3rd party cleans and uninstalls, registry cleans and fixes; nothing worked.)
Eventually, the thing that DID work was to to use an extractor package (like 7zip) on the download package (iTunes6464Setup), and repair or reinstall every program element individually (AppleApplicationSupport64, AppleMobileDeviceSupport6464, etc,) EXCEPT for Apple Software Update. If you try to install ASU from the individual program .msi, you will still get the error message.
To do this:
Download 7zip (http://www.7-zip.org/) and install it. (This is if you don't have an archive viewer already.)
Go to your downloads folder that you used to store iTunes6464Setup.
Right click on the iTunes6464Setup program; select 7zip -> Open Archive.
A new window will open showing you the program install elements.
The big one is iTunes64.msi. You should be able to get that one to install correctly, which will actually make iTunes useable.
Hope that helps you.