I have a 8 Core Mac Pro, I got it around Christmas. It's seemed to be running fast. But then about a month ago it wouldn't start up and it would just sit at the apple logo. So I reinstalled lion and ever since then this computer seems to be running slow. My Macbook Air runs faster then this thing and granted it has a SSD but this thing has it beat in everything else. What should I do? I don't think there is a virus. I have VirusBarrier plus do a sweep every week. What do you think is happening?