I know it a bit of an old thread now but if your still having issues try starting the machine in safe mode and then disconnect and network cables, wireless connections, usb modems. then disable your anti-virus and try running the defrag again.
The reason for removing your network connections is because you will be disabling your AV. AV can stop a defrag along with other services and power saving options that are running. Starting in safe mode should leave most of these services disabled.
HTH
Mark.