05-14-2017, 09:59 AM
I meanwhile solved the issue by making a copy of the working win10 disk test installation and by replacing the contained win10 os parition with the OS partition from the vhd which doesn't boot inside virtualbox. So I have now a vhd disk which contains proper efi/recovery/bcd setup plus the backed up OS partition from the non-working vhd disk and now it boots perfectly in virtualbox. That's why I think it surely has something to do if there's a proper efi/recovery etc. setup inside the vhd disk. An interesting test would be to expand the non-working vhd drive and do it vice versa, so copying efi/msr partitions to non-working vhd and see if it boots as well but I think I'm lazy and won't test this.