Can someone tell me why I cannot defragment my disk? - I go to - start - programmes -accessories - system tools - disk defragmenter: It just stays at 0% although it is seemingly working.
The usual reason for problems with defragmentation is that there is something running in the background which repeatedly accesses the hard drive.
As Fo3nix suggests, booting into Safe Mode can often prevent this.
Alternatively, shut down all running programs as follows:
Press Ctrl-Alt-Delete
(In XP, go to Task Manager).
Now select each program in turn and click 'End Task' for each one. Do this for everything except Explorer and Systray.