Further investigation showed that 21.4.13 added a registry item
called
Path to the registry which added the directory to the path for XEmacs
shells only (not the global system path). Version 21.4.18 does not add
this registry item.
There should not even be necessary to have any paths in the registry,
xemacs.exe should figure out where it is located and use that to find the
location of any related files and folders. It could then set its environment
variable PATH so that any sub-shells/sub-processes can find the xemacs tools
from their inherited value of PATH.