I think people use alcohol to clean the ceramic heads. Not complicated, but getting in
there ...
You could also think about vacuuming or blowing crap out of the mechanism before cleaning
the heads.
Disks give errors, duh. Whatever you use to image a disk, use it as a first attempt, as
that may be the ONLY chance to save the contents. People put a disk in the drive, do a
directory scan, screw around some more. And then the disk is no longer readable. It
happens. Just bang it with whatever program you got before worrying what's on it.
I've never imaged a disk in a usb drive I don't think, can't help you there. I
habe written dos images to external drives though.