I am trying to flush the DNSCache on a win2k server machine via the
command ipconfig /flushdns, but it gives me the error message: "Cannot
flush the DNS Resolver cache".

I am trying to do this because for some reason the existing domain
name that I had registered with Active Directory on my domain server
has been retained somewhere (in the cache most likely) and any
attempts to join machines to the new domain name, give the error
message "cannot find network name";  I assume that there is some
naming conflict here.

You renamed your Active Directory domain? Is this correct? You demoted
the DCs, changed the name, then re-ran dcpromo to re-install AD?

Have you looked in the DNS manager to make sure it has the correct
names/etc listed? Is the DNS service started correctly?

I basically ran dcpromo to demote the DC, then reran dcpromo to
reinstall AD with a new domain name (i.e. trconsulting.com to
trconsulting).

I have looked in the DNS manager to make sure that it has all of the
correct elements, subfolders, etc.  DNS is started.

I am wondering whether there is some other way to "flush" the DNS.  I
am pretty sure this will solve my problem.

I had a similar problem about a year ago. Did exactly what you did,
and the server never worked correctly afterward. Other systems could
not join the new domain, and the server itself generated errors
without putting them in the event log, along with other peculiar
behavior. The official line from Microsoft?

"Reinstall the Windows 2000 Server software and start from scratch." 

Apparently demoting and re-promoting a Win2K server causes no end of
problems, and most technicians I've spoken to on the subject have
recommended simply reloading the OS rather than spending days and days
trying to get it running properly again.

Of course, if someone finds a way to make this work, I'll be
fascinated to see how it is done.

Verteiron is correct on this one. While there probably is a way to get
your problem resolved (for now) and get your computers authenticating
to the new domain name again, I can see you having other problems in
the future, specifically with Exchange and SQL server if you have them
or plan to implement them. If this box was recently installed for the
purpose of being a DC, I would definitely re-format and start over to
make sure it's done right. If you upgraded it from NT4 from a previous
PDC or something else, then it might not be quite so simple. Having
been an NT/2000 server admin for several years and been through many
AD installs, I can tell you that you don't want problems coming back
to haunt you later down the line from something that you could have
taken care of up front.

I'll be happy to research your question further and try to come up
with a solution, but most likely it's going to be a "workaround" that
will probably get your PCs authenticating again. The question is, are
you happy using a "workaround" for your new Active Directory domain?
Just let me know what you would like to do. Thanks.

PWizard
Google Answers Researcher

Well that was sort of the answer I was expecting.  I figured that
somewhere in the system, a setting or parameter in AD is
misconfigured, and there is no external way to reconfigure the system.

Currently, I have used a slight workaround to address the situation. 
Each of my static boxes have had issues connecting to the domain
server (with the error message, "network name cannot be found").  So,
took a far fetched guess, and put a hosts file entry in each of the
connecting workstations that point at the machine & domain ....  (i.e.
DOMAINSERVERMACHINENAME.DOMAINNAME ) and each workstation was then
able to find the Domain Server.  Having just the domain server name
did not work.

As you mentioned pwizard, this is probably more of a bandaid on a
broken leg than anything.  Currently we are using the box on our
residential/work network as a file server / domain controller.  We at
one point were thinking about putting exchange on there, but we tabled
it for a while. I guess when we get motivated, we will just hose the
machine.  And this time we'll image the drive in case something like
this happens again.

Thanks for everyone's advice.  Really appreciated!!