You should change your processor to a virtualization supported one, i.e. VT supported Intel cpus.
indeed, check if you ahve enabled virtualization in BIOS, check the page weather your CPU supports it if still no go, check if there is BIOS update that solves the problem.
Also, check if you do not have any XEN leftovers (see output on screen while booting, if there are a lot more stuff than usual messages, reinstall your router with cd-install or netinstall to reload clean RouterOS without XEN.
if you had xen on that router, then you definitely need to reinstall.