My 2008 iMac (4Gb ram) was running super slow! Well slower than normal :-)))
Lots of spinning beach ball.
Backed it up with time machine.
Ran Disk first aid and it said drive was OK.
Erase HD and reinstalled El Capitan and it still super slow, even with basic install files only. Again when I try to do anything I get the spinning ball and it takes ages.
Any suggestions would be appreciated!