After trying to run through Small Business Server 2011 Essentials install with a USB Drive plugged in , to present the setup with an answer file to start the setup in migration mode , the setup screen stays on “Completing Installation”. The install was running on a virtual machine on VMware ESXi 5.

After retrying setup again, the same thing happened. When it gets stuck on this screen you need to disconnect the USB Drive , either physically or through the Vmware console if it’s a virtual machine. It then runs through the rest of the setup,  then readd the drive when it reboots, and it will take you into migration mode