Debian (Linux) package management is spread out over several other programs..
I am not sure how many cross references there are to the history of your downloads and installs, but there are at least 2 or 3 'main' DIFFERENT programs that collect information both independently, and amongst themselves.
The programs are (but not limited to)..
and of course whatever gui's you have (Synaptic, Kpackage, etc.) which may house separate files on your configurations.
Soo.. I guess, although I am not positive, that the only way to make sure you can do this-- safely, is to start with a fresh install... and keep track from that point on by updating the *extened_states* file(s) for apt.
I know that sounds extreme.. but unless someone has a more, correct and detailed, sure-fire way of doing it, I just don't think you have any other alternatives.. short of learning every aspect of, of every package manager installed (or which was installed).
You could start trying though, by looking in /var/lib.. (apt, aptitude..)
In /var/lib/aptitude for the *pkgstates* file(s).
A couple of programs *might* help.. But I haven't tried them yet:
- apt-cache's many interesting switches..
- * And in synaptic there are *filters*.. which may help... again, I dunno, I never played with them.. but I know if you select 'all' in the main interface menu, it will show ALL packages currently installed (not the meta files.. just the *names* of the programs and associated libs and dev files.
Just out of curiosity.. why would you want to do this? I mean.. there doesn't seem to be any harm in having an account of what was/is installed, on your system?
Either way, good luck and lettuce know