You will have to give us more information about your Iphone, which IOS version it currently has. You can use Jailbreakme.com from safari to jailbreak your phone if your phone IOS are compatible for use with this method. This works and you don't need to use the power button at all.
If you use redsn0w, you need to put your phone into DFU mode and without power button, it will not work.