If you wish to force your Windows XP users to use the Classic Start menu:

1. Copy / Paste the following to a CSM.reg file:

REGEDIT4

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

3. Merge the CSM.reg file with the registry or run regedit /s CSM.reg.

4. The user must log off and on for this setting to take effect.