Install iTunes 12.1.2 on Windows 8.1 x64
Solved problems installing the latest iTunes.
Problem was experienced by myself and a number of other.
After downloading iTunesx64Sepup.exe (for older video cards) from Apple's download site I still had problems getting the installer to run under Windows 8.1.
I had tried removing iTunes and all remnant of prior installations. Tried Revo Uninstaller Pro. Still tearing my hair out couldn't get the install to complete.
Finally, I ran the "Take Ownership" of the 'C:\ProgramData\Apple\Installer Cache' folder on my Windows 8.1 system.
Voila!!! Install now completed successfully and my iTunes is operational again.
iPhone 4, Other OS, Windows 8.1 x64