cannot edit and save
 

hi,

i am using excel 2000. i cannot edit and save a existing file.
the file is not protected,not read only and not shared.
when i open the file, a Microsoft excel window appear saying "File is
locked. In order to save changes to the file, you can either close the file
before making any changes and then re-open it, use Save As (File menu) to
save the file using another filename, or turn off Shared Workbooks and then
save the file."
i try to clear the checkbox on the format cellsprotectionLocked
but still when i click save a window appear saying "Document not saved"

please help