Custom Dyndns with Windows 2008 DNS server

Note that there exist 3 domains for use when you don't want to tell people what your real domain is - example.com, example.net and example.org. If you just make domains up you'll likely pick a domain that really exists, confusing the issue.

As you've just discovered, you should never create your Windows Domain to use a real domain. One option is to use the .local TLD, though if you use UPnP that can conflict - in a work environment it shouldn't ever be a problem however. What you'll need to do is to change your Windows Domain to use a different domain. Once you've done (and I'm not sure how much work that is, but it probably isn't trivial) you'll be able to see your Custom DNS domain.