U can't reboot it u must unlock the screen.. If u want to,log in to ur Hotmail on other device. there are commands there u can choose delete. Reset the phone..
go to http://my.windowsphone.com and reset it from there. I've also heard that entering the wrong PIN enough times will do a hard reset, but I don't know if that one is correct or not. Regardless, the easiest way would be from the web site.