My imac will not boot past the blue screen. It crashed whilst loading a new application which I downloaded from the mac website, had to force a shutdown as it wasn't responding, and now it will not boot no matter what I try.. I have searched for answers on the forums but my mac will not respond to any keyboard commands even with the installation dvd inserted. I don't get the startup chime anymore either. I am now stuck for what to do and have run out of ideas, would appreciate some advice. Many thanks.