I'm running windows xp 64, which is really xp over server 2003, It runs iis6, which is capable of running multiple websites, but the XP version doesn't let me, I would assume this could be changed with a registry edit? any Ideas?
That's a limitation of the Windows XP version of IIS. It's not something you can just change with a registry change (and the license says you can't do that either).
Even thought WXP x64 is really just W2K3 x64, the limitation is still in the product.