I tried rendering something with one of the default HDRI set ups.  It was a little test render of the Robkitty that comes with P7.

Nothing else in the scene, just the robot.

After 4hours it had only rendered a fraction of the cat's head, which was way too dark (I had the thing set to all reflective, with a purple diffuse).

Anyway, I lost patience and cancelled the render.

(AMD2600, 1.25GB RAM, etc...)