I seems dat bios V 1.21 broke the virtualitation settings (VT-X) in A515-51G. If VT-X is set to ON in Bios, Intel Processor Identification Utility reports Intel virtualisation: No. After changing VT-X in Bios to OFF the Intel utility says: Intel Virtualisation: Yes. Because of this, Virtualbox does not support 64 bit-hosts. Hyper-V seems to work properly.
After downgrading to Bios 1.20, all is fine and I can use host-operating systems in Virtualbox in 64 bit mode.
Does anyone have the same problems with this update?