A good friend of mine has a Mac-mini, approx 3 years old. Recently it has slowed to a crawl, soon after a Firefox update. It gets used for a lot of photography storage. Currently it has 2GB RAM installed (with a possible capacity for 16GB). Could any of our resident Mac guys suggest solutions in lay-mans terms please? My suggestion has been a download of AVG for Mac to check it out - and boost the RAM as high as possible. Could someone suggest what % of HD storage needs to be unused to maintain the machines "breathing space"?