deauthorising defunked computers?

goshawk on horseback

hello all,
is there a way to deauthorise defunked or no longer working computers in iTunes?
as at least 3, possibly 4 out of my 5 permitted computers in iTunes are now in some way, either scrapped, no longer working, or defunked in some way or another, so they can't be used to deauthorise themselves.

Join to automatically receive all group messages.