Logon to 2000 Server

I have a Active directory Windows 2000 server sp3. I have
different clients with Xp professional Sp1 and Windows
2000 Professional sp4. When the windows 2000 prfessional
workstation logs on to the domain they go right into the
desktop but when the Xp professional workstations logon
they can take up tp 5 minutes to get to the desktop. Can
you tell me step by step instructions to fix this
problem. The users wait a very long time to hit the
desktop with Xp professional machines.