|If you don't want to use the routines supplied by the OS then you have a problem. You need to directly address the memory of the graphics card and/or its IO ports. But you can't do this from a userspace program; only the kernel can do this sort of direct access as the processor needs to run at a higher privilege level.|
What you need to do is download the DDK, learn how to write a device driver, and then write one to do the job. Personally, I'd use the OS routines. I really can't think of any good reason why you would want to roll your own.