changing default directory for iTunes Library.itl and iTunes Music Library.

Using TweakUI to Move or Create Your Library/My Music Location

Use TweakUI (See: ’Disk is locked’ or ‘iTunes folder cannot be found’ when installing or opening iTunes ) to create a 'My Music' folder in a spot where you desire. iTunes should then find this location and deposit its Library files there, and the 'iTunes' folder and sub-folders as well (if you direct it to).

First, see this Article for some background information: What are the iTunes Library files?

If you cannot see the ‘My Music’ folder within the TweakUI drop-down selection, proceed on to the following:
1 On the start menu go to ‘Run’
2 Type in RegEdit
3 Navigate in RegEdit to HKEYCURRENTUSER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
4 Delete any entry for ‘My Music’
5 Navigate up the tree to HKEYCURRENTUSER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
6 Make sure there is an entry for ‘My Music’ and is pointing to C:\Documents and Settings\[username]\My Documents\My Music (you can edit the value by double clicking it)
7 Close RegEdit
8 Reboot
iTunes &/or TweakUI should now be able to find the folder.