Lets say, you've arranged your desktop icons to look well with your new wallpaper. Someone happens to mess up with this arrangement. Now you have to redo the entire customization. To avoid this mess, you can lock the icons so you dont have to repeat the arrangement.
Locking your icons:
To lock your desktop icons, first arrange them carefully the way you want them to be, then open up the registry editor (Start > Run > regedit)
In the Left pane go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer.
Right-click in the right pane, select New > DWORD Value name NoSaveSettings and press the Enter key. Right-click on the new NoSaveSettings item and select Modify. Enter 1 in the Value data box.
Once you've done this, whenever you restart Windows, your icons will return to their current state.