Here is a story about a Mac customer I had at work once.
A customer comes into the store with a relatively brand new Mac iBook from JB HIFI. He asks us how much to install Windows 7, I quote him up and he goes ahead with it. He asks me to back up some files/documents on the desktop, I back it up from him, install Windows 7, and copy his data across. While copying the data I noticed he had AVG (I don't suggest this), and a few other antivirus/spyware program installers. I hand him back his iBook after paying for it.
The next day or day after he comes back in saying he has got a virus, accusing us for not telling him he need protection, where I said "you had those installers, I thought you were going to use them", his reply "you should have told me anyway", went on like this for awhile, till we finally come to an agreement. I removed the virus, customer picked up his iBook, I then proceeded to tell him about activating Windows - he demanded I do it then and there for him, this was against company policy as it is an agreement between them and Mircosoft, Still did it anyway.