FileEdit

From Gordon's Freeware:

FileEdit allows you to either safely scan through a file or edit one. Allowing the Formatting to show will block showing characters over 126. It is safe to scan any file, but beware making changes while Editing a File can corrupt it, and then activating after could upset your system, unless you know exactly what you are doing. This especially applies to those files in the Windows, or the Program Files Directory. Hex values are shown in editing, but use Decimal values to enter changes.