BIOs points to the bootable drive, this will not change unless you
make a different drive the master bootable drive.

Hd stands for hard drive just like fd stands for floppy. The first
letter for the device tells us the drive type, hard drives have two
types defined by the letters s and h and this is because there are
more than one type of interface. Because windows is on its own drive
(virtual drive) as is Linux, the pointer points to the first track of
the drive, this is not new but the way it has always been.
Grub is a boot utility that allows you to choose more than one disk
drive at start up, the grub simply takes up the first track of the
bootable hard drive and gives you an option of what drive to use. The
computer the OS and the grub or other utility could care less how many
other systems can run on it, only that it has taken control of the
computer.

Windows understands the file system it uses and won't recognize any
other file system, this is a good reason to use Linux native file
system when dual booting for the Linux space. Without special
utilities installed Linux will not write to NTFS even if it knows it
is there. ext3 file system is hidden from windows because it can't
understand the system without a utility to do so. A very good reason
not to use any of these utilities.

On the ubuntu sites documentation there is a chapter on understanding
the Linux file system so you understand how to find things before you
get lost in it. I suggest reading this short chapter to familiarize
yourself as to how things are stored on your system.

menu.lst has comments on the selection for start up defaults, simply
open the list and read it to make your default system start if you
have a preference. You can delete any old lines you are not using and
you can also tell grub how long you want it to wait before choosing
the default for you.

Hope this helps you understand what is happening, if not read the
goods on the ubuntu sites documentation if you want to know more.