iTunes no longer works on Windows XP, apparently due to a change in iTunes security. 16% of Windows users run Windows XP despite Microsoft cutting off large amounts of support and multiple operating systems being released since then. Possibly worse than the initial problem is that at least for now, there is no fix in sight, other than moving off of XP, or iTunes, or both.
VentureBeat has found the likely source of the problem. The issue’s root appears to be that iTunes has updated their security and the update to Windows that seems to make it compatible with iTunes isn’t coming to Windows XP due to Microsoft cutting support. If that is the source of the issue, Apple would have to use older versions of security for iTunes and that doesn’t seem likely.
This is a perfect example of consequences that arise from using an unsupported OS. Microsoft continues to push users towards newer versions of Windows but there are many holdovers. The rumored summer release of Windows 10 may be the final push that causes many to switch but based on previous statistics there will almost always be some on older systems.