Hi, few weeks ago I was still using OSX 10.7 (lion) with 16BG, and my computer was super fast. It is a Macbook pro 13-inch Mid 2012. Recently I installed the newest OSX 10.11.4 (El capitan), so from 10.7 to 10.11 it is a big leap. I made a clean install, erased the hard drive, then transferring my data and reinstalling few softwares (latest versions). So I was expecting the computer to be fast, but I find it surprisingly slow compared to what I was used to with OSX 10.7. Opening files and folders in the finder sometimes takes few seconds with a beachball. Opening tabs and browsing with firefox is slow. Scrolling with whatever program is slow and sluggish. Hot corner is slow. Very often, an action like scrolling or clicking has this little 2-3 second freeze which is really annoying when you are used to a fast OS. I was really not expecting this with 16GB of ram. I tried to optimize the system as much as I could. I Removed all animations, disabled everything unnecessary. Found some advanced advices to improve the speed on El capitan. Also, activity monitor does not show any particular problem. I have an HDD 500GB sata, it is 65% full, and I read it is advised to change for a SDD to improve speed, but still I am wondering how OSX 10.11.4 could be much slower than 10.7, even with a HDD? Or is El capitan designed to force people to buy a SDD? I am not doing anything heavy at the moment with the computer, just internet browsing, vlc, this kind of stuff. Or maybe my hard drive could be tired? But it was working fine few weeks ago and it is not very old. Anyone has had this kind of experience with El capitan? In particular I would like to find someone who has the same kind of configuration as me: 16GB, HDD macbook pro 2012, if your El capitan is fast, then it may be that I have another problem.