Someone on the bochs-developers list mentioned that they use a program called WinImage, from www.winimage.com to read and write disk images (floppy and hard disk). Winimage is a commercial product with a 30-day trial.
If anyone wants to write a tutorial, send mail to bochs-developers mailing list and volunteer.
This section was contributed by Luca Cassioli and Stanislav Shwartsman
I eventually found what all of you were looking for for a long time: a freeware, graphical, win32 compatible HardDisk image editor! It can handle a large variety of formats, but the one you need is VMWARE 2.0 PLAIN DISK: you can import/export to/from bochs images COMPLETE DIRECTORIES!
You can find it at http://hp.vector.co.jp/authors/VA013937/editdisk/index_e.html