Did a reinstall of vcenter server now there is no inventory

Hi all

I had some issues after upgrading from Vcenter server 4 to 5.5.

I decided to start again so I ununstalled all the components including sql

Now that I have done a clean install when I connect to the vcenter server the inventory is blank, when I try to add a host it says the licence is already assigned to another inventory and when I select the host there are no VMs showing on it

so the big question is what did I mess up and how can I fix it?

thanks

Tracy