I assume from your post an external USB HD could be used for manual backup if it is shared? My guess is with a NAS all computers connected to the network can be automatically backed up? What about wireless backup? I actually have 4 computers, 3 hardwired and 1 laptop on my network. My guess is I could backup the laptop wireless but it would be slow. The NAS HD I am thinking of, WD World Book, has an ethernet input but no others, I think. If I connect my laptop to the desktop, do you think I can back up my laptop manually that way? Maybe I should look for another NAS that has multiple inputs. 

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