This looks to me like VirtualBox made the wrong choice and it doesn't have much to do with TinyCore specifically. I presume the warning/error message came from the host OS (Windows) or hypervisor (VirtualBox) and not the guest OS (TinyCore). I'm guessing your host either doesn't have Intel VT-x/AMD-V OR it's not actually turned on. Care to share the make and model of the PC and the exact model number of the CPU?