Visto che con Office 2003 si trova in
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\11.0 \Registration

...e in Office XP (2002) si trova in
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\10.0 \Registration


... azzarderei un

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\9.0 \Registration