iTunes Doesn't Open
When attaching an iPhone, iPod or iPad, or when launching manually, Apple iTunes does not open. Perhaps a quick flash of the window may be perceived. Task Manager shows iTunes.exe running, then closes.
This may occur if QuickTime is corrupt (say, has missing files).
Manually launching the QuickTime Player may resolve this, as it will self-detect the missing files and perform a reinstallation.
Alternatively, uninstall QuickTime and use Apple Software Update to install the latest version.
2016 Update: iTunes no longer has QuickTime as a dependency, and QuickTime is now unsupported on Windows and must be uninstalled anyway. So if this problem occurs, uninstalling all Apple components except iCloud and reinstalling iTunes from a freshly-downloaded copy may resolve it. (Note that uninstalling iTunes does not delete any data from the iTunes library.)