The service named "SERVICES.EXE" (you can see it in the Task Administrator) used 100% CPU due to the DHCP.
I have a 3com 812 OCR router using DHCP and this caused that the Windows2000 seems blocked around 1 second after 5 seconds doing well.
I have solved the problem changing the properties of the TCP/IP of the LAN connection, telling the OS use a specific IP direction, netmask, gateway an DNS servers.
I hope this post help other users with this problem.
Bye,
frapen