[SOLVED] Do i need to reinstall windows if I am upgrading from a g4560 to a core i3?

no, but you should check to see if your motherboard needs a bios update for that specific CPU
id give you a link on how to do this but I dont know what your motherboard is. search for manual if you dont have one. this should provide you with the acceptable CPU's for that motherboard and if you need to bios up..otherwise dont update unless told to.