file sharing problem, can't remove share

I have a Vista Home Basic machine networked with 2 Vista Home Premium
machines and want to share files. On the Basic machine I select folders to
share but when viewed on the other machines I see the shared folders but am
denied access even though permissions have been set for everyone to read and
the owner of the Premium machine is listed as co-owner of share. This works
both ways neither machine can view files on the other. When I go back into
permissions there is a 3rd listing along with Everyone and the previously
selected user of the Premium machine as <unknown Contact>. When I remove
that and select Share it always returns. I can't remove sharing on those
folders now. I get an error message that the folder is shared by another
folder. I can't find where this is true. I've tried to remove all shares
but can't remove the shares for the Contacts folder, the Desktop folder, and
My Documents nor get rid of the <Unknown Contact> in the Permissisons.