Defrag wont start

Hi , I am running windows ME and having trouble starting the defragmenter ,
I have tried start/programs /accessories/defrag , the page opens but wont
start .
Ive also tried start /run /cmd , but the mesage says 'windows cannot find cmd'
A while back I had a similar problem and was advised to press cont /alt /
del and remove some of the items on the list ,
which worked fine , but I cant remember which ones to avoid.
Can anyone help.
Thanks Jim