How to figure what packages were installed from the old installation drive?

[Peng Yu]

Hi,

My old ubuntu system was install in a hard drive, which is not mounted
in a new ubuntu system (not at the /). I want to figure out what
packages were installed in the old system and reinstall all these
packages in the new ubuntu system. Does anybody know what is the best
way to do so? Thanks!

-- 
Regards,
Peng