What should I use Windows XP, Vista Home premium 32 or Vista Home Premium 64 ? Light gaming with this computer since this is my second system, mostly photos, home videos and movies.
Do you already own Win/XP? That would still be a good choice.
If you need to buy an OS Vista Home Premium is the way to go.
32 bit / 64 bit version would depend a bit on the hardware you're going to be using.
An older PC or PC parts might do better with Vista/32, especially if you have a lot of older software you want to carry forward. But for a new build Vista/64 is probably the best choice.