That has always been a problem when web sites make big changes. Not much we can do about it here. Going back through goodness knows how many posts with such a link is out of the question. It looks bad to Google and other search engines, too. Links to "404" pages here "hurts" the ranking for Elsmar. But - I know there are a *lot* of 404 links from over the years in posts in threads. When I come across a 404 link in a post I delete the link and note it in the edit, but there's no way I am aware of literally search and find every 404 link in every post. It would have to be a software solution.
Back around 12 years or so ago there was a program for the Mac which would do that, but only on static web site pages. The pages in the forum aren't static.
Oh, well. It only goes to show how long Elsmar has been around.
Many sites link to pages and stuff on ISO's web site. Links to 404's on the ISO site will be broken on many web sites.