I booted my 2007 imac onto Diskwarrior 5s thumb drive today and was able to run a scan to rebuild the directory. My imac had been unable to boot for a couple of days now and i was trying to rule out any issues with the startup directiry after multiple failed Disk Utility attempts to recognize the volume and/or correct the problem. Once the Diskwarrior scan was complete, a report popped up where you can preview the changes, then click either "cancel" to abort or "replace" to apply the new directory. Unfortunately the "replace" button is grayed out and i don't know how to get it to display so that i can click on it to approve the new directory. Any suggestions? --- Post Merged, Jul 6, 2016 --- This is what the report looks like, except the "REPLACE" button on the lower right is shaded out.