Yes, the HP stands for Home Premium.
I am really doubting that this is a pest. I am running MSE and it is perfectly happy. I usually run the box as a standard user and am VERY careful about what I allow. I make my living fixing computers, and sadly much of that time is spent removing pests. I am comfortable with malewarebytes, combofix, rkill, hijackthis, etc. I WAS wondering if this might be some new badguy I haven't yet seen, but suspect instead that it is more likely generated by a tool trying to be helpful. Maybe something encouraging "greenness" powersaving, either from Windows or Macecraft or Scotty (WinPatrol). It would make the most sense if it were Windows. But so far none of those seem to be responsible. I continue to look for a source of the popup and suggestions are welcome. I have not seen it again, btw, but I will try to avoid a reboot to see if it comes back.