Look you can boot a Linux exactly as you boot a Windows.
The trick is to have a boot loader inside the Linux.
If you Linux uses Grub you can replicate Grub by the command in bash shell (need to be root)
grub-install /dev/hdax where x is the root partition number of the Linux. Use
lilo -b /dev/hdax for Lilo as the boot loader. When that is done. These two lines in /boot/grub/menu.lst (for Grub)
title My Linux in hdax
If your Linux is in hda4 for example then x=4 and use (hd0,3) in the above.
Lilo can boot it too, also 2 lines as
All Dos, Windows, BSD, Solaris must be installed in a primary bootable partition and will have the boot loader in the root partition by default. In Linux it is an option during installation but you can always replicate it later as shown by the above.