OK, I worked this out. Whilst I was playing with this I installed the full iSpy (over some time) on all 4 PCs. I should have deleted the iSpy main program (apart from iSpy server) from the 3 machines I was using as servers & only left the main program on the PC I was using to record onto and view from. I still haven't worked out why Skype caused one PC to BSoD so I just deleted Skype on the grounds that too many BSOD's ain't good... Consider this thread closed.
How to get Windows 10 now: how to download and install Windows 10 even if GWX.exe is missing