I was getting 10 minutes of the spinning color wheel after every key stoke. The fine folks at the Apple said it could be because my mid-2009 mac was too old to run El Capitan and recommended I upgrade the HD and RAM since I can't afford a new computer.
I am a complete tech novice and know very little to nothing about hardware and operating systems, but I followed the repair guide on the iFixit site and was able to install the new hardware (SSD HD and RAM) pretty easily. It was getting OS X onto the HD that was a challenge, but I persevered and now my trusty ole computer is back and I am once again a complete person!
Download a copy of your latest operating system before you change out your HD.