Thanks Tarq,
I spoke to the neighbour this morning and Emailed him the link for Malwarebytes.org so by the time I see him this evening he should have a scan under his belt and, as you suggest, a rootkit scan will be next.
We'll see what they both turn up and proceed from there. As you say, it really is a bit odd that I haven't been able to find the .exe, although I can't rule out operator error.
Thanks again,
I'll post findings later today or tomorrow AM,
N o t a