I bought my MacBook Pro back in mid-2010. It's got 4gb ram, a 2.53ghz processor, and I'm using 150 of 500gb of hard drive storage. About 2 weeks ago I upgraded to Mountain Lion. Since then I've seen more spinning beach balls in those 2 weeks than I did in the previous two years. I've read about ML slowing down performance and this is very frustrating. What can I do to get back to my original performance, where apps opened in a flash and web pages loaded instantly? Does it make a difference if I did a clean install of Mountain Lion vs upgrading? By no means am I an IT guy so if we could keep it simple, that would be great. Thank you.