Upgrade hurdle: phantom packages won't purge, won't upgrade

[Michael Bell]

I'm stalled while upgrading from Potato (2.2r6) to Woody (3.0) using
dselect: apparently from nowhere, my system thinks it has
kernel-source-2.0.0 and kernel-headers-2.0.0 left unpurged. dselect
presents some error messages from postrm scripts claiming files not
found.

dpkg --purge NNNN halts with the same error. I dug out the
distribution CD that the packages came from (dated 1996!) and
attempted to reinstall, remove and purge the packages, but dpkg
--install NNNN also halted with similar messages.

None of the --force-* options seem relevant here.

It appears to me that sometime over the past few years, something has
been deleted that shouldn't have been, leaving an entry in a database
somewhere that I'm now tripping over.

I'm not familiar with the innards of the dpkg system, and don't really
want to learn if I can help it (I'll forget it all before I have to
use it again). Can you suggest a solution or guide me to specific
documentation (I have already skimmed the package documentation at
debian.org).

Thanks, Michael.
Perth, Western Australia.

(All the above is a cautionary tale: I should never have smiled so
confidently when I fired up dselect...)