Complete Deletion/Reinstallation of Downloaded Package

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http://askubuntu.com – I want to know how to delete every file installed by a package using either aptitude or apt-get and then re-download and re-install that package completely again. I've tried doing aptitude reinstall apache2 apache2-doc after running aptitude purge apache2 apache2-doc but that doesnt work. What I did was I deleted my /etc/apache2 directory thinking I could just reinstall it (I was having PHP integration issues) but now whenever I try to install it I get the error "invoke-rc.d initscript apache, action "reload" failed." Any advice will be helpful. (HowTos)