Dell Inspiron M731r not starting up. Help

Hello my Dell Laptop does not want to start up it just stays on the dell logo. I was going to upgrade from windows 8.1 to windows 10. It downloaded windows 10 then it restarted the laptop, where it said getting updates. It finished getting the updates then restarted the laptop and its been on a black screen with Dell in circle and nothing else no loading bar underneath it. Its been stuck on that screen for almost 2 hours, I can also hear the fans start going at what sounds like full speed for a couple of seconds then slow down. I dont want to shut it down and start it up again because im afraid it'll mess something up. What can I do?