I have used Defraggler for long time , no problems, after installing v1.5 I was defragging my C/ and Defraggler crashed two times, finally after defrag is finished my system is works very bad, music sound shocking, files accesed very slowly, start up time twice longer than before.
I defragged C with integrated Windows tool, now C responds much better, some files couldn't be defragmented though, but on the D drive still same problem, for example if I play music from folder on C works OK, if I play from D drive sound is chocking. I will try to defrag with windows drive D. Looks like Defraggler v 1.15 made major mistakes during defragmentation, hope that developers will fix that issue soon. I do not like to use windows tools, in fact I do not like windows at all , forced to use it as many others , looking forward to some free , open source OS.