Hi: I have a customer that has a 2010 MacBook Pro that was sluggish and slow. I ran Scannerz on it and the hard drive is bad. I/O tests on the cable came back clean, and there were no weird readings like system faults, so the logic board is OK too. Everything indicates it's limited to the hard drive and it isn't severe, but considering it's age I'm recommending replacing it. This guy is using El Capitan and before testing I noticed the fans were coming on a lot, particularly when web processes were present. Although the drive was bad, it wasn't so damaged to be useless. I suspect the HDDs slowness and the fact that they run a hotter than an SSD may be contributing to the heating problem. Can anyone out there confirm that the system will run cooler, or at least cool enough with an SSD for his fans to stop coming on so often? I'm not really sure the fans coming on so often is because El Capitan is loading the CPU so much or because of heat generated from the hard drive.