you can look in the registry..but if it has winME on it now I am pretty sure it will have the WinME product key
run "regedit"
then look under
hkey local machine/software/microsoft/windows then click on "current version" so that it opens up in the right window pane....then if you scroll down some on the right you will see the "product key"...but as I say it is probably the ME key