Disk Editor is a free low level hexadecimal editor

Disk Editor tool uses a simple, low-level disk viewer which displays information in binary and text modes at the same time. You can use this view to analyze the contents of data storage structure elements such as: Hard disk drives, Floppy drives, Partitions, Other objects.

The Main Features: Enhanced template view; Side-by-side Compare and Edit; Fields coloring with data in tooltips; Extensive exFAT support; Fast navigation points; Filling selection with a pattern; Unicode support; Quick Disk Info; Bookmarks; Data Inspector.