I have a mid-2008 MacBook Pro and (as you’d expect for a machine this old) its running really slow. It has 4 GB of RAMM (and can’t be upgraded beyond that), a 500 GB hard drive with about 100 GB of free space and running El Capitan. I’ve given up on it for writing music and editing video. Now its just used for word processing and web surfing. I’ll be getting a new MBP in March but until then, what can I do to optimize speed and performance on this dinosaur?