As long as you've got a copy of the Snow Leopard disc you should be good to go.
Unless you're running programs that require it, I don't know why you'd choose Windows XP over Windows 7 but if it floats your boat then go for it.
yea i do, I have a cd that i got from a family member who owned a 2008 macbook and I also have a OS 10.5 cd for a mac upgrade which i bought in 2010 (idk why but i did)