iBook machine name conflict on Windows Network

Guys, I'm have a bit of a problem with connecting my iBook (OS X 10.3) to my work Windows network. I connect using DHCP and get an IP address fine and off I go on the network.... but I also appear to be picking up a 'machine name' which is conflicting with a Windows laptop on the network that has a different ip address.

Before I connect to the network my machine name is 'sdreed', but once the network is on I become 'D456xxxx.domain' which is odd as all the Windows boxes have assigned names and this is not passed out by DHCP. And for some reason I get a machine name that is already in use when there are only 10 machines on the network.

Bascially I want to stop picking up a machine name....... or at least get a new one.