Problem: After creating a new VM machine, it gives the error " IP address is already assigned to Microsoft virtual bus adapter, not allowing to assign IP address

Resolution : Microsoft virutal bus adapter is hidden if you open the device manager from the control panel , the hidden devices will not show.

please open command prompt with run as administrator

set devmgr_show_nonpresent_devices=1
start devmgmt.msc

go to view, click show hidden items --- uninstall the the adaptar and assign the IP address.
it will work now.