First off, the ASPNET user account isn't performing any access because it is
local to the server only and is therefore irrelevant.
I'm not even sure how you would perform such a task. Typically, any upload
mechanism that you would perform through a normal web page would require a
file input type. I'm not sure what the limit is on the number of files.
Typically the upload is for one file at a time so I don't think it's
possible to grab an entire folder as it's not a recursive operation. There
is a trick to doing more than one file per upload form, check out:
http://the-stickman.com/web-development/javascript/upload-multiple-files-with-a-single-file-element/
for a great example.
Basically though, I don't think there's an easy way to do what you want.
JavaScript wouldn't have the permissions to rummage around and grab the
favorites and you can't upload folders themselves. Not to mention the fact
that each browser out there handles favorites completely differently. I
don't think this is going to be one of those things that will be worth a lot
of time investigating as I'm not sure it's do-able.