XP Pro networking

I need help… I installed 30 XP Pro computers. I noticed that they were quite slow on the network so i checked their IP’s. DHCP is giving out the same IP for all 30 systems? The IP is a valid IP in my scope (10.6.122.18) but i cannot figure why it is doing this? If i assign static IP’s all is well. I check DHCP on the 2000 server and it registers 10.6.122.18 to one of the 30 systems but does not list any others??? Any ideas??