Have now downloaded and used smartftp. I can now view and access all four sites,that part of the problem is now solved,thank you all.
The part of the problem still remaining is that the sites are still linked in some way, in as much as, if I delete a file on one site if it exists in the others it is deleted in them all.
I am thinking now of backing everything up, and deleting contents of the four sites (all on the same server)and re-uploading them one site at at a time.(fortunately only one site of any great importance to me)
I will hold fire for a little while in case anyone can suggest another or better solution.