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Thanks for all your help. Yes, they're all on 'WORKGROUP', file and printer sharing is turned on and, as I say, the XP PC is talking happily to the Windows 7 laptop. The XP laptop can see the other computers, but I'm appear not to have permission to use this network resource and I'm directed to the adminstrator (which, as the only user of that computer, would be me!)
I'm intrigued by the Windows Userid and password business. Could this be my problem? And, if so, can you tell me how to do this?
Thanks in advance.