1. Start > Run > Notepad.

2. Paste the following:

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"ForceClassicControlPanel"=dword:00000001

3. Save it is 'ForceClassicControlPanel.reg' (without quotes)

4. Double click ForceClassicControlPanel.reg > You will be prompted to add the information, click yes.

Note: See also Force Use of Classic Control Panel (Xp Professional)