|I'd suggest running your command (which looks correct to me) then checking your folder shares under computer management (compmgmt.msc from the run dialog). |
From here, check the share permissions and make sure they make sense and are created as expected.
What version of Windows is this under? If you create the share manually and test, does it work?
Also, as an aside - make sure the Guest account is enabled if you're using it for this purpose.