Avast boot-time scan keeps running?

I’ve had to look this info up a few times, and it’s always hard to find, so I’m putting it here.

If avast’s boot time scan runs every time you start your computer, it’s likely that something like Spybot S&D is preventing changes to the registry, and the boot scan can’t be disabled.

In the registry, you can remove it manually to prevent it from running on every boot.