I have been using a MacBook Air for a few months now. In high school (5 years ago) we used Macs. The last few years I have been using...windows...I know its sad. Anyway my girlfriend told me her uncles iMac got a virus that was bad enough that they had to replace it. How real is a threat of viruses to the Mac OS? I saw they had Norton Antivirus in the Apple Store is it necessary? Adding to that how is the threat of spyware? Other than that what maintenence things do I need to be worried about? Also I have noticed that every once in a while Safari seems to run slow for a period of time. Before and after this it runs really fast. I am on a wireless network using a cable internet connection. Could there be something wrong here? Thanks for the help!