You need a Registry Editor since this is a registry entry.
HKCU = HKEY_CURRENT_USER
HKU = HKEY_USERS
HKLM = HKEY_LOCAL_MACHINE
HKCL = HKEY_CLASSES_ROOT
You can use the powerful free Task Manager. There's a registry editor implemented.
You can download it here:
http://buzzdev.net/index.php?option=...=read,27,15027
The upxed version is just smaller since it is compressed.
Best regards,
Jens