What will you do when the Mac OS X Yosemite not working ? You must have got panic and worried about all the data that is saved in the Mac drive. This problem may occur due to various reasons such as any error while updating the operating system over the internet. There may be some internal corruption issue that can be caused due to abrupt shutdown or due to some malicious files saved in the drive. The Mac OS X Yosemite not working situation can also be faced due to drive issue when it is damages or something. The drive can be fixed by using the disk utility and then you can make the restore the operating system by using the recovery partition. Lastly you may have to reinstall the operating system if the Mac OS X Yosemite not working. The data however can be recovered by using the time machine backup but if it is not working then you can use the Mac data recovery software. It scans the whole Mac drive and retrieves the list of lost files which can be selected for recovery. So you should download the software and use it after resolving Mac OS X Yosemite not working problem.