Hi,
I think to convert the physical Windows to a VM you will need a specific tool depending on the virtualizer that you use, for simplicity and best results probably you need a paid product...
Its also possible to do that like if you are working with a real PC by creating an full backup image to a network location, boot the VM using the Rescue Disk and restore to image to the HDD on the virtual machine, but for this to work you need a software with the option to restore on different hardware because Windows inside the VM will not see the real hardware and must be adjusted to work on the new hardware presented by the virtualizer.
Don't forget that Windows to run inside the VM will need a new license...