To have the dual boot, you need 3rd party software, linux, or an
older version of windows (eg. XP) already installed when installing
a newer one (eg. Vista). You also need to have a clean partion or
another hard disk you are installing the new OS on.
The start menu in XP will be like a 'brand new' one as you
installed it from scratch, unless you upgraded it from win 98/2000
on the same partion.
As for the drivers, it's specific only to the OS. So the drivers
you installed would be only for that OS. For example, your DVD disk
in the DVD drive may be able to read in ME/2000/XP/Vista/Linux but
not in earlier operating system like Windows 3.1/95.