Just over the past week, our 21" 2010 iMac is running super slow. I backed up the entire computer overnight on another back, erased the hard drive, and tried a fresh install of Mac OS X. Still runs super slow. The spinning Beach Ball of death takes 30-60 seconds to execute simple task like opening apps and opening and closing folders. I think the hard drive is bad and needs a replacement. I did upgrade the RAM to 12GB with Crucial about 2 years ago. Any other ideas I should try before wasting my time and opening it to replace the HD with a SSD? Thanks in advance.