Question : IP address conflict

I just set up a new windows XP PC on our network.  It uses DHCP to get the IP address.  I get a message on the PC that says there's an IP address conflict.
(1) if it's DHCP, how can it conflict?  I thought DHCP only assigned available IP's?
(2) even though it says there's a conflict, I still get on to all network and internet resources, but I can't ping the IP address or the system name from another PC on the network.  It just times out.   Why can't I ping it if it's an active IP and is otherwise functioning properly?

Answer : IP address conflict

Normally happens if an IP in the DHCP range has been statically assigned without a reservation being made in DHCP.