the simple conclusion is that
the software you have or had
can be traced back to its origin
because of the keys in the
registry/database, whether the
keys are active or orphaned.
so this is one of the reasons
for keeping outdated data out
of the registry file/database.
however, different registry
cleaners utilize different
criterion for removing keys.
for example, the one care
safety scanner version and
then running eusing utilize
two different methodologies
for determining keys that can
be removed.
once the keys are removed they
are not recoverable.
however, the registry and the keys
it had can be restored via system
restore or from a back up.
another point to make is that
simply deleting files or folders
from your disk is the snake oil
because unless the space is "wiped"
cleaned and "replaced" with data
utilizing specialized software, then
that data, which is presumed to
be deleted, is in fact fully recoverable.
and yet the above is not totally
secure, because some software
that "wipe" away deleted data, simply
relocate that data to a different place
on the disk.
-----------
because you specifically asked about
cookie data inside the registry; its easy for
you to check for yourself and develop
your own understanding by clicking on:
start>run>regedit
then go to the menu and use the
"find" option/feature and enter
any criterion that you are interested
with.