I was using my Mac normally. I tried to open iTunes and got an error. I decided to restart the computer. Restarting was going normally, but at the stage of entering username and password, Mac tells me that my startup disk is full. I proceed, Mac recognises password and it gets me to the regular screen and mouse arrow appears. Nothing happens then. No icons, prgrams, nothing. I can't delete anything as I have no icons. What should I do? I tried rebooting few times but get the same thing.