Thanks for the information, I shall certainly be looking more closely this board to ensure it's not going to start damaging whatever it's connected to, +ve wise.
Anyway, your queries prompted me to check out the connections and here's a funny thing. How you'll laugh.
This board is fundamentally for PIC18F4550 development and prototyping. The PIC18F4550 has USB connectivity, which is why I chose it for my experimentation.
So you'd think, well, I did assume this, that the damned USB socket would actually be wired to the only two pins that the chip uses for the USB data. Nope.
Although I originally did fit the correct 20Mhz crystal (I bought a bulk lot from eBay to replace the 10Mhz it came with).
Sigh. I've now wired up RC4/RC5 (how spooky, I've just seen the response by bitfogav) and of course, it works as intended. So, it only took a year to work out why the PICkit2 wasn't writing to this board (wrong way round) and the same amount of time to understand that this prototyping board is not pre-wired but has the capability to allow USB connectivity (but allows you to use RC4/5 for other purposes).
Gosh, I'm laughing so hard. Manic laughter, teetering on the edge of hysteria.
Anyway, thanks everyone for all the posts and pictures and nudges, the project builds, loads and works just fine at address 0x0 and Windows can now detect it too. Now I can get on with what I wanted to do...