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This should reformulate and extend this question http://forum.osdev.org/viewtopic.php?f=1&t=27227

I need to dispatch data from one storage to MBR of another.

I have an usb/cd and I want the MBR to use the devices storage in CHS or LBA mode.
I read somewhere that it is automatically emulated. Is it true? If it is not, how can I emulate it? If it is, how can I switch from emulated device to floppy (or another emulated device) inside my computer?

Learn to properly use INT 0x13

Did you try yet?

I read this http://www-pc.uni-regensburg.de/hardwar ... EDD_11.PDF, but I can not find there anything about manipulating USB/CD by 13h.

Because you didn't try: http://lmgtfy.com/?q=int+0x13+usb
Because you didn't try: http://lmgtfy.com/?q=int+0x13+cdrom
And because I know where the manual is: http://www.ctyme.com/intr/rb-0715.htm