I don't know, possibly. Have you run AV and anti-spyware scans to see if there's any malware on your PC? There's obviously something not right somewhere. Some things you could try: 1. Make sure that you haven't got any other programs running when you try to defrag. 2. Temporarily disable your AV progam and see if you can defrag then (don't forget to re-enable it). 3. Try running Disk Defragmenter wih your PC in Safe Mode If none of these works and your scans show no serious malware, the only thing I can suggest is that you go to the Hijack This logs forum, read Andrew's post near the top and post a log there for analysis.
Madeline.
-------------------- "Power tends to corrupt, and absolute power corrupts absolutely." Lord Acton, 1887.