Default [Q] Nova launcher installed, Sense still pops up

Hi. I recently purchased the Nova launcher, and from time to time the HTC Sense launcher rears its ugly head. It usually happens if I access the settings menu and return home, and I have to launch Nova launcher manually.

I don't plan on rooting or installing a custom ROM yet, and would like to know if there is any way I can keep the HTC launcher from appearing ever?

Thank you