So in the last month or so, my Mac has decided to become very slow. It takes forever to load pictures and videos, sometimes even websites. I've tried repeatedly to download MacKeeper in order to clean up my hard drive, but whenever I try to do so, I get an error message. I've tried to manually delete files that I don't use and have cleaned out my cache because I figured insufficient space was the main cause for the slowness, but I don't understand how so much memory can be used already on my computer (granted I've had it for 3 years, but there's only 22 of 111 GB left and I don't have any kind of games or lots of videos or memory-hogging things in the hard-drive...just pictures and music and word documents)...please help with suggestions etc. so using the internet and trying to do things other than type on my computer aren't so frustrating! Thanks!