I seem to have killed my new mac mini or at best locked it up. About a week ago I installed Windows 7 so I could access work documents on it. All went well until after a couple of days I noticed on start up when I held the 'alt' key I didn't get the option to select which operating system to start up. It just defaulted to the last one used. I then had to shut down and try again, typically after two or three attempts I get the option to select the operating system. Call it an old windows habit but after a session I do shut down the Mac, no reason for it to be on as it is not running any torrents etc. However, last night I did not shut it down. I can't remember if it was left in windows or mac because I was chopping and changing between the two operating systems. This evening I switched the Mini on but there is nothing! No activity on the screen at all. I get a single power up chime and the green light is on the mini but that is all. I have shut it down a few times and held the 'alt' key but nothing happens on screen. Any ideas on what has gone wrong or what I can do to correct it? I hope the graphics card has not died! I have quickly checked the monitor and lead by connecting to my laptop and all is fine there. Thanks in advance for any suggestions.