Third Party hooks - how? and more importantly, where?

Where do third party apps hook into AutoCAD?

I have several loaded and have noticed a couple of things.

1. On the textscreen, they are the first thing loaded.
2. If I create a new profile, and try to remove them, they always come back.

If I search my hard drive for any files that have their name in them, I
don't find any of the normal customization files. I have search through the
registry, and it may be in there, but I haven't found where they would load
from there.

I am trying to get a totally unadulterated Profile from which to work with.
But no matter what I try, these apps (which I do want to keep on the machine
for other profiles) keep loading.

Examples include: ManuSoft's SuperPurge (which I have noticed has a hook
into the S::Startup function, but something has to load for it to get
there), DosLib (once the ARX is loaded), and several other ARX files, that
once loaded on a machine, don't want to unload themselves. SuperPurge is the
only one to hook into the S::STARTUP function.

Also, how do they become "unloadable"? The appload command will show a
bunch of stuff grayed out and some of these are third party apps that are
grayed out and can't be unloaded. But, I say, if they got in there, somehow
they can come out. I just don't know how yet.

Oh, and while I am asking a bunch of questions, what does this section of an
ARG file mean:

<snip>
__BEGIN_FIXED_PROFILE_STORAGE_R16__

<Profile><StorageRoot><AcApData><AdUiTools><ToolsInfo><Tool
CLSID="{D5CF410D-
etc.
<snip>

I am assuming this is some of that XML stuff. Where does this get stored
when you import a profile? A search of my registry for one of the CLSIDs
turned up nothing.

Thanks for any bones you can throw this way and FYI I am using R16

-Fred.