Back when Mac Classic was the Operating system for Apple there was a good book that was almost required if you wanted to fix Macs called SE Repair and Upgrade Secrets. It was written by Larry Pina and it went into detail about how to repair and upgrade a Macintosh Classic and Macintosh SE personal computer, without spending more money than would be required to buy a new one.
We got bit by the Linux Bug pretty early after reading this line, "I don't know how any company is going to make money with Linux or what their Business Model will look like, But I know this. Its really hard to compete against Free"
Our first version of Microsoft was DOS 1.0, Now its Windows 8. They are losing a lot of market share, not something anyone predicted would happen but Apple has done everything right. However we will always have to support Microsoft and we know it well.