A long time ago I installed Windows 8.1 on a secondary drive on my Mac Pro 3,1. One day windows said that the trial version was over and that I had to activate windows but I had no activation keys so I left it like that. It said it would restart every 2 hours automatically and that if I wanted it to stop restarting automatically I had to activate it. I was fed up of having to manually select the drive to boot from (Alt key while startup) so I decided to set the Windows drive to default (Ctrl while selecting drive). Some minutes ago I tried to boot to Mac again but something strange happened: The apple logo appeared just as always but something else appeared that wasn't normal, a loading bar. It would load one eighth and suddently disappear. Some seconds later the computer would shut itself down and nothing more. I tried several times but it would alwais do the same. My theory is that the fact that I set the Windows drive to default messed something up. Now I need to know how to fix it. Any ideas? Thanks. P.D: I'm writing from windows right now since it is still working, the one that doesn't work is the Mac drive.