Login to Win 2000 domain is so slow

I recently configured a LAN with a domain. There are 21 Pc’s connected.

all the machines are configured to same network configuration. all the machines has same hardware configuration.

But 5 machines takes almost 10 minutes to login to the domain. i couldn’t understand why 16pc’s takes less than 30 SECOND to login to the domain, 5 pc’s takes almost 10 MINUTES.

can someone give me a solution.