From Wsms

Volume Boot Record

http://members.tripod.com/~averstak/fatdox/bootsec.htm has some information about the format of FAT partitions.
http://www.wolveslug.org.uk/wiki/backing_up_and_restoring_a_master_boot_record_mbr has user-oriented advice regarding mbr and vbr.
http://en.wikipedia.org/wiki/Booting
http://pcsupport.about.com/od/fixtheproblem/ht/newbootsector.htm using fixboot.
http://mirror.href.com/thestarman/asm/mbr/GRUB.htm GRUB assembly code.
http://en.wikipedia.org/wiki/Windows_NT_Startup_Process
http://www.geocities.com/thestarman3/asm/mbr/NTFSBR.htm NTFS Boot Loader Secrets