[1] This is not the case with Linux: you can always
put an ext2 filesystem in a partition labeled FAT and set it
up with no problem, but then Windows will go into sulk mode...
[2] Another of DOS/Windows' limitations, when
Windows 95 first came out, was that the FAT16 was unable to
handle partitions of over 2 GB, whereas hard disks with far
higher capacities already existed, hence the need to use an extended
partition. FAT32 corrects this "problem".
[3] In fact, this diagram (and those that follow)
is not quite accurate: at the end of sector 0, just after the partitions
table, are two bytes which determine whether the disk contains a
partition table or not. If there is one, these two bytes will have the
values 0x55 and 0xAA, and otherwise 0.