Whilst it
is possible to boot off either HDD, not many boot loaders can do that well, the reason being that normally your PC will boot off the drive that is top of the boot order
in the bios. So in effect, you are asking the boot loader to swap the order of drives as defined in the bios - every time.
The situation gets worse if the two drives you refer to are on different channels - as one being IDE the other being SATA for instance.
Just for a laugh, I include this link to the main boot loaders
http://en.wikipedia.org/wiki/Comparison_of_boot_loaders and a quick glance at that will probably put you off the whole idea.
I have tried GAG in the past, which works fine and is easy to use, but does not cope (or did not then) with different channels as I remarked above.
As other posters have said, Virtual box is a fairly good solution to this, where the second (virtual) OS can occupy the whole of the second drive if you so desire. The main need is a lot of memory and a fast CPU, as well as very common and well-supported hardware.
Alas, a second reading of your original post makes me suspect that you are thinking you can run both OS
at the same time
while still having the 2ed running the server??
That is not possible with dual booting and I am not too sure it would work in virtual box either. The act of running a
server or several inside the same box rather depends upon the
host operating system being designed for that (such as VMware) as far as I understand it.
However LifeSteala says he runs a game server in Virtual box, which means his host OS is probably Windows, although it could also be Linux or a Mac.