In answer to the subject title's question, in Windows ME you use the Users or Passwords tool in the Control Panel. Beyond that you can delete the matching .PWL file that I often find in C:\Windows.
The other issue seems to be a networking problem and you need to work on that.
I had an Me PC and an Xp notebook working properly to share the printer on the Me Pc and shared files on both computers. While on vacation, my son reloaded Windows on the Me PC, and then put his user ID and a password into the Me PC for Windows Networking. After we came back from vacation I have been unable to get the printer and file sharing going again. Is there a way to remove the Microsoft Networks User ID and password from the Me PC? I know his user ID and password for Microsoft networks on the Me PC.
I think that is the problem, since the notebook says "M007 is not accessible. You moght not have permission... The list of severs for this workgroup is not currently available". Note the Me PC indicates the printer and files are shared because of the underlying hand.