iphone 3gs passcode blocked, dont have itunes....help?

hi i have a iphone 3gs had a laptop etc, my friend was messing about with it & blocked the passcode, i dont have my old laptop that my iphone was sync 2, but i do have access to a computer, is there anyway i can just download itunes & restore the iphone to its orig settings. i dont care about loosing any of my contacts etc