INT 21h

Hi everyone.
I was making a little ASM project when i came across a problem.
My program reads a file from the hard disk, it uses INT 21h to do so, but INT 21h does not work if DOS is not loaded, and my project is supposed to run without DOS, so how can i load a file into memory without using INT 21h ?

Thanks.

Here's an example how to load a file and execute the program code in it.

http://www.geocities.com/mvea/bootstrap.htm