My screen went blue so I shut off my MAC. When I turned it back on it prompted me to login. I log in then quickly it flashes "logging in" then returns me to log in screen. I put the OS X Install disc in and checked hardware did the hold C but did not click on the disc. Instead I clicked on hardrive. Now when I try to use the disc or hold down any keys.for prompts at startup it doesn't work at all. I've unplugged it and held down power at plugin. Nothing is working. I changed the password when I got the install disc to work that one time. Now when I login in, it says logging in then blue.screen and back to the beginning.....SOS....I need help....I am not that savy.