I use to monthly defragmentate the harddisk, to ensure an optimal state of running of FS 2004 and other programs.During the 2 last defragmentations, this tool refuses to go any further than 86% and then blocks the running defragmentation, so that I have to reboot the computer.It then regains its normal actions as if nothing wrong had happened.Has anyone among the computer-technicians an idea what could be the cause of this strange phenomena?Thanks in advance for a solution!Paddy.

hmm, do you scan the HD for errors before defragging?

Yes, I always do.Paddy.

anti-virus software interference??

You probably have too much other junk running at the same time, like the above mentioned av program. Shut down everything that is not essential.

I want to thank all of you giving your advice for my problem.Meanwhile I have solved it, thanks to a hint of Zevious, which brainstormed my mind.I run checkdisk once more, now shutting down the comp after finishing checkdisk. After restarting the show, I run the defragmentation tool,which finished for 100% with a final report!The difference? Formerly I started the defragmentation process after checkdisk right away in the same session. Apparently one has to shut down after checkdisk and then restart to the defragmentation tool to be successful!Thanks again for your support!Regards,Paddy.