How to Find a Missing iTunes Libraryby Stephen Lilley
An iTunes Library file contains the general information about all of the songs in your iTunes Library stored in a single computer file. If you accidentally move or delete this file, the next time you open iTunes you will be greeted with a blank screen as opposed to all of your favorite songs. As long as you are sure that you haven't deleted the file and it's just been accidentally moved, you can find it again in just a few seconds.
Click your computer's "Start" menu. From here, select the "Search" option.
Type "*.xml" into the search field (without quotation marks) and press the "Enter" key. ".xml" is the file extension of iTunes library files, and "*" indicates to your computer's search utility that you want to find any available files with that extension regardless of what they are called.
Right-click the appropriate file in the search results and select "Open Containing Folder." This will open the directory in which the file currently resides in a new Windows Explorer window. From here you can make a note of the directory of the file and either move it back to where it is supposed to be or point iTunes to its new location to restore your library.