EasyBCD provides an advanced GUI that makes it relatively easy to modify the Windows Vista bootloader, allowing you to add and remove entries to it for dual booting with other versions of Windows, as well as Linux/BSD, Mac OS X and other operating systems.

Depending on your system configuration, creating a multi-boot system can be as simple as clicking a few buttons (but it may also require copying and editing of system files). The program can backup and restore your current boot settings, allowing you to undo any changes if you run into problems.
Download the program from here.