Someone on the bochs-developers mailing 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
Ben Lunt wrote a utility for Windows to manipulate flat disk images and their included file systems.
You can find it at https://www.fysnet.net/ultimate/index.htm
This is a Windows Dialog based utility, with source, and includes the following items:
Partitioning: MBR, PMBR, eMBR, EFI GPT
File Systems: FAT, FYSFS, LeanFS, Ext2/3/4, SimpleFS, ExFAT
Inserting, extracting, and deleting files from said file systems. (some file system support is currently read-only)
Checking the integrity of said file systems and other items.