I am trying to make a very small operating system of simply printing hello world. I am using pen drive in place of floppy here. the program of assembly language i am using is

http://www.joelgompert.com/OS/h.asm

I save it in h.asm and then convert to bin file using nasm assembler by command
nasm c:\h.asm -fbin -o c:\h.bin

then i write it to my pendrive using debug by using the following commands
debug c:\h.bin
-l 0
-n f:\h.bin
-w 0

Now everything works uptill now.

When i reboot my pc making pen drive as priority boot device. Then i get the error
Error reading disk
Press any key to restart

Then i get message-
There is no boot data in your device.

Where the things are going wrong. Please help.