Launching a PortableApp at system startup: How does Lightscreen do it?

I want to be able to launch a PortableApp at startup, on a computer where I do not have administrator privileges, without placing a shortcut in my /Start Menu/Programs/Startup folder.

I see that Lightscreen is already able to pull off this trick, but I cannot figure out how it does it. I see that at Lightscreen's config.ini file includes a startup=true/false line, but how does Windows know to look there at startup?

Does anybody out there know the trick Lightscreen uses, and if there's a way to replicate the method with other apps?

Thanks in advance.