I have a pretty old macbook, late 2007 from the serial number. It has been getting slower and slower over the last few months. I realize the computer is on the older side but I'm hoping to be able to use it for another year or so since I just browse around online and use email and stream videos. I brought it to a computer repair place to run a diagnostic and they said the RAM and hard drive are fine. They said there are some corrupted files and are claiming that is the reason the computer is running slow. They are asking $95 to clean out these files. Is that worth it? Or is it something I can do myself? I'm a little skeptical from what I've read in other threads that this is really whats causing the problem. Any advice or suggestions?