So my Mac crashed today. I don't know what I did, it was running just as good as the day I bought it this morning. It started running real slow, I powered it down and now it won't even boot up. The only thing I can think of is that I tried viewing a video in quicktime and it led me to an Apple site to download a plug in and ever since then it's dead. I don't know what to do. It boots up with a gray screen and apple logo but thats about it. I can hold shift after the boot up tone and that will get me a blue screen.