A program that will boot with the computer can only be made in assembler. If you want to know how to make one just search google for "bootloader". Then when you have that, you can start making the rest in C++ (not C++.NET), but assembler is still recommended for core parts like the kernel. A hello word program like that is not hard as long as you have basic understanding of assembler.
If you want to know hardware specifications then manufacturers should have some resources, like Intel for example has a lot of resources about working with the processor.