Dual boot question (switching between operating systems)

Is it possible to switch from say Windows XP to Vista at the touch of a button, but having the old OS active in the background? Im not a fan of virtual PCs, just I have 2 operating systems at the moment and the only way to access the other one is restarting the PC, is there a way to bypass this so I can work on XP, switch to Vista and then back again without restarting?
Answer #1
I dont think it can be done virtual pc is the only way I knpw
Answer #2
You can’t run two OSs at the same time with out using Virtual Box or something similar. Even if it was possible, you would have to have an awesome system to handle it all too
Answer #3
I was thinking if something existed along the lines of the “switch user” system