Defrag not working?

I just finished a defrag-run. Immediately after the disk was again shown as fragmented. Activating defragmentation started the process all over again.

The process started with 20% fragmentation and ended with 19%.

What's happening?

Hi mdlang, and welcome to the forum.

Do you have any exclusions set, in particular the ones depicted in this screenshot ...

http://forum.piriform.com/index.php?showtopic=38165entry231327

I'll just mention the thread that screenshot is in is about a different problem, but the settings are probably relevant to yours.

Is there enough free space on your drive? For better results you need about 15% of free space.