I have a G4 and am unable to start it up. I cannot open the disk tray so do not know how to bypass the hard drive in order to start up my computer. I think i might be reaching my quota on available memory space on the hard drive. I thought it might be the battery and removed it for an hour and put it back in. A Mac person suggested that once to me, a long time ago. I'm using OS 10.4.11 I also tried keyboard short cuts such as pressing shift button when restarting or the X key. Can someone help me?