Are you getting Mac blue screen at start up ? When you switch on your Mac system it should give you a gray screen which in process searches for start up drive. After that you will get the blue screen as the Mac loads the boot information from start up drive and then the desktop is displayed. But sometimes Mac start to give problems and get stuck to Mac blue screen on start up. If you are getting the blue screen that means your system has correct power supply, run its preliminary self test but can not load up the data from start up drive. Your start up drive might be suffering from different type of issues which you can try to fix mac blue screen on startup using Apple disk utility or by starting up your Mac by starting it in Safe Boot mode. If they do not prove to be useful then you can certainly use a third party software that is recommended here. The software is able to restore all the data of your mac after you fix Mac blue screen on startup . The Mac will start up uninterruptedly after using it with all data intact.