While it is used the version recommended according to S.O works perfectly. If you install the 5.1.4 (or superior) in Yosemite or El Capitan, can damage the disc, so that there is to reformat and to reinstate everything.The system of updates of the program, must have had this in account.The last compatible version with Yosemite and Capitan is 5.1.3 and now it does not try to update to a later one, as it must be.It is a good program, and it helps enough to maintain discs in sequence. But from time to time, the updates are not without risk. Due to him, I have had problems several times, the last ones with the passage to Yosemite,and it makes a pair of months with these incorrect updates of iDefrag.In addition, it is possible that some problems that I did not know to identify also came to use one more an up-to-date version of the indicated thing.