OK, you PDC is a win2k3 server, it needs to be the primary DNS server for itself and all workstations/member servers on the network (AD integrated).
If your XP doesn’t get the IP address from the DHCP, you need to set the primary DNS to your Win2K server as well, you can set other external DNS as your secondary or tertiary if your Win2K3 server doesn’t give you lookups for outside your network. This is to ensure that all workstations know where to find the AD server to get authenticated.
Some additional things you can look at on the clients are as follows:
Local Security Policy
look down the list for “Microsoft Network server: amount of idle time required before suspending session – default = 15 minutes”.
Right click and Properties.
Set this to an obscenely large number of minutes.
on the same list… find:
“Microsoft Network Server: Disconnect clients when logo hours expire”. Right click and Properties.
Set at “disabled”
Let me know if this helps.