The layout & contents are stored in the registry values found under:
"HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Streams\Desktop"
"TaskbarWinXP" holds the settings for the taskbar & any additional toolbars attached to it. "Toolbars" (if it exists) holds the settings for any toolbars on other edges of the screen.
The tricky part is, these values are only read at login, then retained (and modified if you change the layout) in memory throughout the user session, and only written back to the registry when the user logs out.
So, to backup a layout, you need to log off & back on after making any changes and before you export the registry key. If you want to restore the key from a backup, you would need to:
Open regedit & task manager
Kill the shell by clicking 'Start' -> 'Shutdown' (turn off computer),
press & hold <Ctrl> + <Alt> +<Shift> & click the 'Cancel' button in the Shutdown dialog.
Import your saved key.
Restart explorer via Task Manager -- 'File' -> 'New Task (Run...)' -> type 'explorer'
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Good Luck,
Keith Malke
Microsoft MVP [Windows XP Shell/User]