Reboot update

hey every one I have a problem I hope some one can help me with . Ok I was updating my computer (vist) and while it was updating I acadently turned off the computer and now every time I turn it on it keeps trying to update 3 of 3 and then it reboots and does the same thing over and over again and I don't know what to do. If you have answer pleas e-mail me at titin_3000@hotmail.com