This error message can be caused by several,
but closely related issues:

Most common (Microsoft Knowledge Base article Q148729 ):
You have been connected to a Novell Netware Server, using the NDS-service,
and have deleted the "Client for Netware
Networks", and then deleted the Client, but
NOT the "Service for Netware Directory Services
(NDS)"
or:
You have FIRST deleted the
"Client" and THEN
the "NDS-service".
It seems, that it is very important, that you FIRST
delete the "NDS-service"
and THEN the "Client
for Netware Networks".
To fix the problem: re-install the "Client for
Netware Networks", restart,
then delete FIRST the "NDS-service",
THEN the Client.
(deleting in a different sequence leaves some updated files,
which belong to NDS) on the system, they are NOT replaced with
the original files, as it should be (see
Microsoft Knowledge Base article Q149757)
This error message is also displayed in some cases, when
installing real-mode ODI drivers with the VLM redirector (Microsoft
Knowledge Base article
Q136006)
Another possibility is related to the "Microsoft Exchange
Windows Client",
versions 4.0 and 5.0 ( see Microsoft
Knowledge base article
Q150388 ).