I wrote most of this back in the 80s, but recently have added new features. It started as a BASIC sector editor, but slower portions were re-written in assembly and new features were added (trace the DOS file chain, tachometer, create autorun.sys, etc.).
It's now available on my Atari 8-bit Utilities page: http://www.crowcastle.net/preston/atari/
I hope to add double-density support once I get a drive that supports it.
"Disk" 4.0 released: Sector Editor and much more
Moderator: Atari Frog