Mine is also not a solution but my friend was able to do a dual boot of two different OS (windows 7 and Ubuntu) on his self built computer. According to what I could tell, he connected two different motherboards together, with two different hard drives and place them all in one custom made tower. They all connect to one (three actually) monitor and you could see him switch between two different OS environment by doing some kind of click and drag from the corner of the desktop. How he actually did this, I have no clue, but after googling it there were others who did something very similar (hardware-wise).
Just to let everyone know, the performance of his computer did not boost 2x or whatever just because he rigged two motherboard together. It was literally know different from having a single mother board in a computer. The only difference was that the tower was larger. Whether he used a special chip or software for connecting the motherboard together for the dual boot, I am not sure. However, it looked cool. However, he told me he took the whole thing apart and created to different computers. Something about, it is not very efficient having two OS running at the same time even if they have their own resources...
Oh yea. Sorry for necroing the post.