A client has a 2009 Macbook Pro 2.23 ghz Core 2 Duo with 8 GB ram and a new SSD hard drive. First of all, I haven't been able to find a link to download a later OS, in spite of seemingly easy ways to do it when you search online. What happens every time is you arrive at the latest Mac OS Sierra page - and this computer doesn't satisfy the requirements. When I search I find many reports that say Snow Leopard is the best OS for this computer, that El Capitan or whatever will be slower. The client wants El Capitan to deal with continual feedback that her OS needs upgrading for the things she wants to do. There are two questions: what do you think is the ideal OS for this computer and how ought I go about upgrading if I want to go that route? It is possible that she might have to purchase a lion or mountain lion or yosemite or whatever disk to upgrade farther than SL. It appears that apple sells these disks for $20 or so. Try as I might, I have not found a link to download a later installer. Sierra is a bully and it appears to prevent the display of earlier versions of the installers.