When I add a file to iTunes library, does iTunes make a copy of it? If yes, where is the copy saved?
If the option "Copy files to the iTunes Music folder when adding to library" is activated, iTunes makes a copy. 

The default storing location is:


Windows 7: \username\Music\iTunes
Windows Vista: \username\My Music\iTunes
Windows XP and 2000: \Documents and Settings\username\My Documents\My Music\iTunes
MAC OS X: ~/Music/iTunes/