Which itunes version is compatible with iOS 4.2.1 and Windows XP?

I've got an old iPhone 3GS running iOS 4.2.1. And I've got an old PC running Windows XP. My son's 7-years-of-age. And I simply wish to give him a phone to play with and synchronise with this PC (mainly music and photos) -- just for fun. So, would you please tell me which itunes version is compatible with iOS 4.2.1 and Windows XP that I may install on this PC? Thank you indeed for your assistance.