Getting Mac prohibitory sign start up error? If you switch on your Mac, the first thing it performs after the hardware tests,is to verify a startup disk that has any version of OS X on it. If the computer system is not able to search out your internal hard drive, it starts looking for somewhere else on a Thunderbolt, FireWire, thumb drive, Universal Serial Bus (USB) disk, or on DVD. Here your Mac generally finds your hard drive, which consists of your operating system, and the startup process proceed with the perceptive Apple logo. If your Mac is not able to find your hard drive or doesn’t find on it what it requires to boot OS X, you see the fearful Mac prohibitory sign start up. You should think of the prohibitory sign as Mac’s mode of saying, “Please provide me a start up disk.”If you face any of these warning icons, you may be required to do some troubleshooting. You may use different alternatives, such as using Disk Tools and First Aid, zapping the parameter RAM (PRAM), and a Safe Boot should be performed. But in all this process your data is lost because of incapability to be recovered owing to the failure of booting process. You can still recover the data by Mac data recovery software. By this recovery software the loss occurred due to Mac prohibitory sign startup error is resolved.