Firstly, GlenR & ExtremePC: I appreciate your assistance.
Now, this is where I'm at:
This morning, after using my RF keyboard to standby my main HTPC, it would not boot. I went into BIOS & had to reset the boot HDD priority due to an issue with, I believe my SATA power connector (whoever devised the connectors, both power & data, for the SATA interface should be

******rated G. Suffice it to say they are, at best, poorly designed).
Now, back to my monologue. Not realising this at first, I had reimaged using my last Ghost image. This took the system back to a state of using 'simple file sharing'. I also redid my networks via the wizard. The only thing I changed was to rename my bedroom from "2nd HTPC to 2nd-HTPC, as I had read on one of the network sites that having spaces could cause issues. Guess what, all my PCs were visible from all locations.
I went onto MCE & still no media files were visible. I could play them on both Zoomplayer & WMP6.4 (classic). I tried manually opening a file from WMP10 & it stated that it could not play the files but gave the option to try. They played alright, but am surmising that because they don't open by default then MCE cannot read them.
OK. Time to upgrade to WMP11, as my Matroska-contained AVIs open automatically on my main HTPC. Damn.....!!!! I had setup my bedroom HTPC not to be internet connectable to save any dramas with updates etc. Can't install WMP11 as it won't validate.
Bugger. Am in the process of Ghosting this setup & will redo my 2nd-HTPC's network to be internet-connectable. But I am getting there.
