Right now I am running a Windows 2003 network in "Windows Server 2003 interim mode". I have have 2 w2003 DC, 2 NT4 DC and no w2k DC. I have about 100 clients. I want to switch to "WIndows Server 2003" domain functional level. I know that NT 4 DC are not supported in this senerio. I need to keep the NT 4 DC up until I can move the apps that reside on them over to different servers. I don't care if the NT 4 DC aren't able to authenticate users or perform and DC functions in the new domain functonal level. I was just wondering if there are adverse effects in keeping 2 NT 4 DC in this new domain functional level. The 2 W2003 DC servers should easily handle all the DC roles in my network. Must I purge all the NT 4 DC before continuing?