Have you seen the Mac pro blue screen recently ? The is quite an annoying situation that will not let your Mac computer to start and you can not perform any operation with it. You will be unable to use any application or use the stored data. The reason why you are getting the blue screen is that there is some corruption issue in the file of the operating system that can be due to the internal error or the corruption of the Mac volume where the files are saved. You will have to fix the drive and then reinstall the operating system or simply repair the OSX files. Whichever the case is the files can be lost from the drive then you can recover it with the time machine backup. If the the time machine not working then you can use the Mac data recovery software .This allows you to scan the Mac drive and get the list of files that were lost. You can see their preview and then restore it by selecting them. So download the software now and use it.