I'm really happy to see another guy tinkering around a machine. Why don't you get into electronics like the MIT hackers of the 60's and improve the circuitry of your mainboard?
The Intel Microprocessor Barry B Brey - This is where you should start reading.
The C Programming Language by K & R - This is the C Bible (The book is written by the creators of C language!)
I'm NOT Intel bias, well only a little bit because the Intel is soooo cool!, but that said, the Intel book is mostly about the 0x86 family of processors that drive the embedded systems and supercomputers (Home PC's) of today! Well worth a read to get familiar with the Architecture of the PC.