Recently we migrated a Windows Domain from a 2003 server to a Windows 2008 Server. When it was time to demote the 2003 server we ran into an error about the Domain Controller holds the last replica of the following application directory partitions.
DC=TAPI3Directory,DC=OurDomain,DC Microsoft TAPI Directory
The procedure to remove this directory was quite simple. First we open a command prompt and type TAPIcfg show.
This gives us the TAPI partition name which you should note is a fully qualified domain name.
Once you have that then you type:
TAPIcfg remove /directory:PartitionName /Server:PrimaryServerName
You might be able to leave the /Server parameter off but it didn’t work without it for us.
If you need to create a TAPI application directory partition you can reference this Microsoft page.
You can also type TAPIcfg help at a command prompt.