By Alfresco Explorer I tried to delete a website folder of which I was the creator and owner. I received this kind of message (error):
Unable to delete Space due to system error: 081128781 site deletion is not allowed. Attempted to delete workspace://SpacesStore/a108830e-9f50-4291-b78a-ef4859b7f57f
Its quite simple, you can't delete sites through alfresco explorer.
The background to this is a few years ago we would have people deleting sites through explorer and causing chaos. Sites are an Alfresco Share thing. You should delete a site from Share.