You can use virtualization, which means you are running one of the other operating systems on top of the other, at the same time, thus switching between the two is like alt-tabbing between programs. If you have 2 monitors connected you can run one operating system in each monitor at the same time using this methed. But if I was you I would run linux as the main operating system and vista as the virtual one, this will make your system far more stable than windows virtualizing linux.
See
http://www.vmware.com/ for more info.