Can't install iTunes 12.1 on Windows 7 64-bit.
This seems to happen with every fifth or sixth iTunes update, and iTunes is incapacitated until the following update. In this case, the error message is as follows:
An error occurred during the installation of assembly 'Microsoft VC80.CRT .type="win32" .version = "8.0.50727.6195" HRESULT: 0x80070091
ZT desktop computer-OTHER, Windows 7, 60 GB SSHD; 1 TB HD