Eduardo,
A combination of Bobby's and Paul's responses are needed. IF you have
SP4 on the DC you can perform a dcpromo /forceremoval (this will allow the
machine to become a lowly member of a Workgroup again, but will not remove
the lingering AD "metadata" for the DC; this is why you need to run through
Q216498 that Bobby mentioned. This method has a couple of caveats that are
different from a normal dcpromo: 1. Normally when you demote DC it becomes a
member server, dcpromo /forceremoval makes it a member of a Workgroup named
Workgroup. 2. A normal demotion will automatically transfer any FSMO roles
to another DC; dcpromo /forceremoval does not. (you will need to seize these
roles later) If you do not have SP4 on the DC, but have SP2 or later, you
can download the Q332199 hotfix that will give you the dcpromo /forceremoval
option.
Adam Arndt