Mac personal Computers are simply brilliant as it is developed and designed by Apple Inc. However, users encounter with many problem as they work on Macintosh Computer. Mac OS X prohibitory sign is one of them. It indicates serious trouble in the smooth running of the Mac machine. We can also call it as a warning sign. Yet, Prohibitory sign is common issue reported with Macintosh OS. Mac OS X prohibitory sign appears on screen as deep colored circle with a diagonal line in middle of it. It suggests that there is some thing wrong with Mac system. May be the component between the hardware and software is not at the proper position. Or we can say that during installation some critical component are missing. In this situation the system is unable to boot and hence causes loss of data due to Mac OS X prohibitory sign. If you are getting this particular error on Mac, formatting or re-installing the operating system can resolve this issue. However, if you do not want the data to be lost, opt for Mac data recovery software. It can recover the lost data very easily. It can also recover the deleted and missing files or corrupted data even in case of Mac OS X prohibitory sign.