I have not played with "dual booting", which is usually used to start a choice of different operating systems and gives you a menu at boot time. But i think that would work. Try a Google search on "xp dual boot".

I agree that the BIOS is where you would make a fixed change to the boot order. Watch your first screen for a clue to how to get into your BIOS, if you're not familiar with that. It should have a quick message like, "F2 for setup..." or some such. In the BIOS look for a menu item called "Boot Priority" or just  "Boot" or such.