The 3 Intel Manuals. Order them from developer.intel.com, click on Literature centre then scroll down the next page for pentium 4 processor and find a drop down menu, select manuals and then ok button, then order them, putting in your details. Also, they are free so no costs. Same applies for AMD cpu's. Their manuals can be order, however i ordered mine some time ago but still haven't recieved them but in the past info from AMD was a little slow so they might still arrive. Wait 3/4 months
The Intel manuals will tell you all of what you need about the pc in connection to an os and programming but it's shown using assembly language. Other information about os design and such is best found on personal web pages such as the tripple failt club and osd.
MMURTL 1.0 - Book about developing a 32bit operating system through the eyes of someone who fully developed 1 (MMURTL). It's also explained in a more practical sense and not all thoery which is what most osdev books are, all theory.
Any other programming/hardware book is usefull. Try searching on amazon.com for 1 and order it (not sure which countries they offer to though, if not all.)
Try an IRC channel called #bw on server irc.nullus.net
/server irc.nullus.net
/j #bw
once joined type "@find <bookname or keyword>" then download. Figure out this procedure for yourself. Many books available, not all tech related. They are books in general, so don't expect to find exactly what your looking for. MMURTL is not on these servers. For that book look through the history of this msgbrd and there's a link to get it somewhere
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A web site that might be helpful, personally i don't use it myself, but it has some books about c/c++ and other tech topics.
www.informit.com. sign up and search through the books for a topic. They do charge for most books but last time a checked some were free to read online. You can order them but free ones online aren't for a free price when ordering.