I tried replacing the ROMS on my Mac 128k motherboard, because I couldn't get a system disk to boot - tried two different disk, one 'new'. They didn't seem to work, of course....put the old ones back in, and now the internal disk drive is spinning at full speed before I even put the floppy in, and catches the receptor on the disk, but makes a bit of an unnatural screeching sound when it does. Not sure what I did. It wasn't doing this before. The Mac screen is flashing a disk icon with an X on it....anyone?