Stop ALL other software from running first.
This includes anti virus software.
If you have Microsoft Orifice this can cause problems if the Find Fast utility is installed. This utility builds index files of all files on your drive, can take hours to finish and will stop defrag.
The following works on Win98 but I do not have a machine with ME installed in order to check it.
Reboot the machine and force it into SAFE MODE. In '98 keep pressing the ctrl key whilst booting.
This will start Windoze
without loading the mass of drivers and other software.
Then run the maintenance wizard.
This will allow most to scandisk and defrag.