People using iTunes to synch their various apple devices sometimes feel that it would be better if you can have separate media libraries for different apps. This feature would be quite useful too if you have multiple people using the same account for synching (Easily resolved by creating another user account for windows,), who rather find it inconvenient to switch between accounts.So here is a solution for you !

1. Make a iTunes shortcut to someplace convenient, like your desktop
2. Press the Shift key while clicking the iTunes icon
3. You get a option to create a new library or choose from existing ones

Click to Enlarge

There you go, a simple solution for a simple problem!