What is wrong with the windows one?
Nothing I know about. I used it often in the past.
I think most users want something different, faster, more functions, goodlooking, because they are bored to use Windows Defragmenter.
One thing I know for sure, no defragmenter changed anything on my computer, not faster, not better, no nothing.
Nevertheless defragmenting your harddisk is necessary, sometimes.
I use PerfectDisk (payware), but I never noticed any improvement, using it, although Raxco claims it's fantastic.
The only software that changed my computer in a sensational and good way, was FirstDefense-ISR, but that is not a defragger.
