Virtual Network Settings.... are grayed out

I've just installed VM WARE SERVER with Red Hat Enterprise 4 as the host OS. The machine is a Dell Poweredge 2650 with Dual Xeon 2.2 GHz processors and Dual NICs. The problem I'm having is that the Virtual Network Settings under Host are grayed out. I had planned to run several virtual machines in different subnets but I'm unable to allocate network resources as needed.

Thanks for any help.