We have recently encountered a problem with networking our Windows XP
machines with our Windows 2000 Server.  We recently purchased about 10
XP Professional machines and joined them to our network which was
exclusively Windows NT4.0 at the time.  The machines were joined to
the domain and were doing fine.  We had a server meltdown and totally
rebuilt our network with Windows 2000 server.
The NT4.0 server that broke down was an IBM Netfinity 5500.  Model
number was 8660.  Machine type was 41U.  It had a P2 processor with
128M of RAM.  It was the domain controller and ran print services,
file services and DHCP services.  Like I said eveything seemed fine
when this was the setup.
That server broke down and we replaced it with several Windows 2000
Server machines and configured a new domain.  The domain controller is
an IBM 300 PL.  Machine type is 6565.  Model number is E2U.  It has
128M of RAM.  It is running DNS services and has active directory
installed.  We have another IBM machine that is identical to the
primary domain controller.  It is running DHCP services and does not
have active directory installed.
Our main problem is that in the new domain the XP workstations take a
very long time to log into the network.  They have all been joined
into the new domain but when you log into the network it can take as
long as 5 minutes to get fully logged in.  On the old network it took
no longer than 30 seconds.  What is our problem?

Just a couple of hints - I'm not a google researcher, so don't want to
take away from whomever is putting the full effort into this.

I'm an infrastructure/AD architect, MSCE+I with 10 years NT/2000
server experience, so feel at least qualified to help out here.

1. First observation - the 300PL is a very underpowered computer to be
running as an AD Domain controller, especially with only 128MB of RAM.
It could be running off virtual memory (thrashing the disk, swapping
pages in and of virtual memory, which could slow it to a crawl and
explain the slow logons)

2. It looks like you completely lost your original domain when the PDC
(Primary Domain Controller) went down, without first being able to
remove the workstations from the domain. If after you built the new
domain, you changed the membership of the XP workstations from one
domain to another, they will still believe the old domain to exist,
and time out trying to contact it before presenting the logon screen..
Try this.. on XP workstation, remove it from the domain completly, and
make it a member of a workgroup. Reboot, then re-add the workstation
into the new domain. See if this fixes the problem.

3. DHCP is tightly coupled  with DNS and Active Directory in a Windows
2000 domain. I don't have time or space to go into details, but you
really need to build a second Active Directory Domain Controller, and
assign the DHCP role to this server. A domain controller has four
roles, and a single DC shouldn't be perfoming more than 2 of these
roles. As it is your DC is doing all four, and doesn't have a backup
in case you lose it, in which case you'll be back to scratch.

In order, I would do this:
1. Add as much RAM as you can do your existing domain controller.
2. Build a 2nd domain controller on a reasonably fast computer with at
least 256MB of RAM and remove your NT server.
3. Try removing the XP workstations from the domain into a workgroup,
then re-add them.

Good luck,
Tim

Windows XP and Windows 2000 Server with Active Directory use DNS to
find your Domain Controler - On each XP - Place the IP address of your
Domain Controller in the "DNS" section of "Local area Conections
propeties" dialog.

For those who need the location:
Right click "My network Places"
Left click "Properties"
Right click "Local area connections"
Double click "Internet Protocol (TCP/IP)"
Click "Advanced" button
Click "DNS" tab

Good Luck - This will work!