Peter,
You can use your favourite search engine to find out. Also the topics related to interfacing hard disk have been discussed many times earlier.
Coming to the MBR (Master Boot Record), it is a an area (The first Sector of the Cylender 0 and Head 0) of the hard disk (independent of the OS. It only contains the volumes informatin).
Anyway, here is a link to get your doubts clarified...
Master Boot Record Reference

Hope you get what you want.

-Harsha