Okay so I'm using Windows XP and when I try to analyze my drive I get an 'analysis failed' message and when I try to defrag it I get a 'building file list failed' message. I've tested it on the same computer on a thumb drive and it worked but it won't work for my main drive.
Try this : Action menu >> Advanced >> Check drive for errors.
'Verify drive was unable to complete successfully' after reaching and progressing through the second phase.
Windows key + R (that will open the Run... prompt) >> type cmd >> type chkdsk /R
If needed, reboot.
Okay the chkdsk went through but defraggler still won't work.