The only way i see this possible is to create a partition from C:\ and make the partition big enough to hold Vista on it and then just load it. But i gotta say i dont afvise this cause it may cause confusion to the computer. if u wanna try it out propperly get another hardrive and install it on that instead and remove the other one u have everything on it and put the other one in the one that u want to put vista on it. and play around that way. Or you can make the new drive an external drive and try that way.
