How can I activate an old iphone without sim? I have set it up as new iphone and it has registered by wifi with my itunes account but cannot get it to activate with itunes (I am using a WIndows XP PC).
You can't, it's that simple. You have no choice but to get a sim card...borrow one from a friend/relative? If you phone is carrier locked, the sim must be from the carrier the phone is locked to. The sim need not be activated, but it must be valid & present for activation.