Q: how to make a bootable dos usb?
A: rufus can help on this (it has its own msdos.sys command.com...)
   just download the app, and install on windows to make it work

   http://rufus.akeo.ie

Q: where is chkdsk.exe?
A: no need dos chkdsk, you just type in windows cmd chkdsk c: /r then next reboot will do

Q: step to ghost backup?
A: 
 login windows then chkdsk c: /r
 reboot
 system will check c:
 reboot then go to usb msdos (or freedos), then ghost

Q: whereis freedos
http://www.freedos.org/

Q: get image file then what
A: rufus can help on making bootable dos usb