rem: regs.eax = 0x800;
add: regs.eax = BIOS_GET_DRIVE_PARAMETERS;
context: get_number_of_drives(uint8 *_count){	struct bios_regs regs;	regs.eax = 0x800;	regs.edx = 0x80;	regs.es = 0;	regs.edi = 0;	call_bios(0x13, &regs);	if (regs.flags & CARRY_FLAG)		return B_ERROR;	*_count = regs.edx & 0xff;	return B_OK;}