Win95/98/Me

Dos based Windows OS's include Windows 95, Windows 98 amd Windows Millenium.
Rrename to .isoDOS01 - CD files will be on B: drive. 
See RMPrepUSB Tutorial 117.
See blog post here
 
You can also make a .imgPTN file.
 

Notes

Win95/98/Me are very old. They will therefore only run on very old systems with small IDE hard drives (or BIOS configured for Legacy IDE) and less than 1GB of RAM. DOS can get very confused about large hard disks and systems with large RAM memory!
 
Even if you manage to get it installed, you will probably not be able to run a browser or get audio working. Graphic swill also be limited. No USB access, etc.