Try Fix unexpected quits or launch issues in iTunes for Windows - Apple Support (document retired, archived copy) and test the behaviour in a different user profile or with a different library.Delete the iTunes shortcuts from the start menu, desktop, task bar, or similar, then repair iTunes from the programs and features control panel.Try disconnecting your computer from the Internet before running iTunes.Again doing this once may sometimes help. Try holding ctrl+shift as you launch iTunes so it opens in safe-mode.Some users were finding that with the 12.6.1.25 build, for example, they had to use this method every time and modified the shortcut accordingly. Doing this once may fix certain launch issues. Locate the shortcut for iTunes, right-click on it, and select Run as administrator.Exit the BTTray.exe Bluetooth utility if installed.Remove any SD card that might be in a card reader.
If iTunes is apparently installed correctly try the following in turn until iTunes opens/closes/reopens/connects to the store normally: