apt-get: how to remove old config files?

[Stefan Salewski <Salewski@physnet.uni-hamburg.de>]

Hello,

to remove a package completely I have to use something like
apt-get --purge remove packet.
If I forget option purge, config-files are not removed.
If I try 
apt-get --purge remove packet
after
apt-get remove packet
to correct my mistake apt-get complaints because
packet is not installed.

To remove old config files reinstallation of the packed
and subsequent removing with option --purge should work.
Is there a better way?

I ask because during my first debian-testing installation (two
years ago) dhcp-client was installed automatically instead of
dhcp3-client. I fixed that at that time manually by removing
dhcp-client and installing dhcp3-client. But I think I forgot to
use --purge at that time, so some old config-files exists.

Best regards

Stefan Salewski