To change SCSI controller to Paravirtual on an existing Windows machine

1. Add first a new SCSI controller VMware Paravirtual

1. Create a new disk of 1Gb and assign it to the Newly created SCSI controller

1. Validate and initialize the disk in Windows, this will pre-install the driver for the controller
2. Shutdown your VM and change your primary SCSI controller to Paravirtual

1. Power On your VM
2. Remove the new SCSI controller and the new disk