I am trying to add a DHCP server to our NW60SP4 network. When I run
DNIPINST.NLM, I enter my credentials, after which I see "Error occurred
adding NDS schema extensions. Error = -659."

Per TID 10011112, I checked for the presence of SYS:SYSTEM\NDDPREFS.DAT
and SYS:ETC\DNS\ROOTSRVR.DAT, and they are there.

I have seen that setting up DNSDHCP can fail if the master replica is on
a 4.11 server. We did a slow migration from 4.11 to 6.0, in the early
stages of which the master replica was on 4.11. However, 4.x has been
gone from our network for a couple years now.