Hi,
Are you using the VMWare Standalone Converter 4.0, if so then you will be able to convert VM that are in ESX/ESXi 4.0 to VMWare Server.
Select the destination type to be VMware Workstation or Other virtual machine and the VMWare product to be your VMWare Server - could be either VMWare Server 1.x or 2.x. You will also need to provide the name of VM and location where you want your converted VM to be.
I have converted many ESXi 4.0 VMs to VMWare Server 1.0 using the Standalone converter 4.0
Hope this will help you solve your problem.
Regards
Nikhil