Randy B. Singer has been on a number of mailing lists that I subscribe to for a long time. I’ve never seen him steer a member wrong.
He states that ” It seems like barely a week goes by without me hearing about a user whose Macintosh has suddenly slowed to a crawl. I’ve helped a number of users troubleshoot the problem, and it turns out that the problem isn’t caused by just one thing. To help users whose Macs have suddenly slowed down, I’ve created a Web page that lists a number of troubleshooting steps that they can take to address the most likely causes of their slowdown.”