I have a MacBook Pro (2010) running Yosemite, 4 G memory, that is barely running some days. I looked in Utilities for a way to diagnose and fix this, but I was not finding what I need. Can someone recommend how to speed this computer up? Desktop photo icons often don't even load the photo --- just some generic icon. Page scrolling sometimes has long delays. Many of features take forever to get moving. Thanks.