No reset button, but you could try unplugging it from the wall and then plug it back after a minute or two. I would try a different outlet or at least plug something into the current outlet to make sure it still works. If you have a surge protector between you and the outlet ( and you should ) unplug it and try straight to the outlet.
No power isn't time to panic, all your info (pictures) is on the hard drive probably ok, just can't get to it.
Possible problems power supply, faulty fans, bad expansion card (modem, video)