I had a tier 1 tech that was having an issue with a client's PC and when he had me come over to look at what he was doing, he was in the registry. I was listening to the steps he took to get to that point, and I asked if he had rebooted the machine yet, he said that the customer had said they did. I was like, have YOU rebooted the machine yet? He said that hadn't, so I told him to do it, problem solved!