When you right click the Start button, you can select Open, Explore or Find
options. To lock down this option, rename the key [HKEY_CLASSES_ROOT\Directory\shell] to [HKEY_CLASSES_ROOT\Directory\shell.lockdown] and rename the
key [HKEY_CLASSES_ROOT\Folder\shell] to [HKEY_CLASSES_ROOT\Folder\shell.lockdown] . There is
nothing magical about the lockdown extension. Don’t delete these keys, just
rename them. If you want to put the functionality back, all you need do is to
rename the value back to “shell”.