You may want to include a total partition of your hard disk in these libraries in Windows 7. An example will be more appropriate to understand the situation:
Suppose, your Windows 7 is installed on partition C and you use D drive to store all your musics; particularly, if you were an user of previous version of Windows (say Windows XP). Now, if you want to include all the music files of that D drive; you have to copy-paste or cut-paste the files. That might create another problem itself. If the disk space of C drive is less (or closer) than the space you need, you simply can not do it. Moreover, as always, storing anything in the same partition that of operating system (C in our example) needs frequent backup for fear of losing data (format, upgrade to next version in future etc.)
It is very easy. Click Start button. Then click Computer:
The in Computer, right click on the hard disk partition you want to include in the library of your choice; hover the mouse over the option “Include in library” then select by clicking the library you want:
This is it.