I've bumped up against this one a couple of times but being as I don't update iTunes often I had forgotten the fix. To help you out and of course so I can reference this later here's the fast way to get around this that actually works.
1. Download iTunes64setup.exe from Apple.
2. Extract the exe using a program such as WinRAR.
3. Run the installer. Once it stops and asks where iTunes64.msi is simply point it there and the install will continue and complete.
Now one more thing...
I have seen even this not work. If that's the case simply run the new iTunes64.msi from inside the folder you extracted and it will bypass the need to look for itself and will install over and upgrade your existing iTunes install with no loss of information.
Hope this helps out. It sure saves a lot of time messing with Microsoft Fix-it (doesn't work) or doing registry edits (doesn't work).