Thanks Aura,
the memtest is showing errors ( in red-similar to the example on the link you sent).
There is only one memory module 4GB RAM with two available slots. I will try the other slot, but I suspect the memory module is bad, so if the slot switch doesn't achieve a better result. then I will order two new memory modules, to increase RAM to 8GB (the max for system), and to have the ability to remove a bad one if the same occurs in the future and still have a functioning system.
Feel free to comment if any of my assumptions/suggestions are dumb!
Is there anything else we can do at the moment, or do I need to resolve the memory module/RAM first ?
Thanks