General   (General discussion, talk about anything.)

Getwom you beat me to it The /f parameter can only be used on a drive that isn't in use by Windows though. If you try to run chkdsk/f from Windows on the drive that Windows is on you will be told that it can't run now and you will be asked if you want it to run the next time you reboot the PC.

Greyhound, could you try pressing the CONTROL ALT & DELETE keys together to bring up the Task Manager, clicking on to the Processes tab and looking for chkdsk in the Image Name column.
If it is there right click on it and select End Process from the menu, then try to do a Defrag again.