Heylo and Salaam
Does this site run on apache? If it does it might be wise to include a small .htaccess rule redirecting all old forums.understanding-islam.com links to the current URL.
A case in point is this post. I often spend some time reading old posts, and it can get a little irritating if links are all dead. I can give the .htaccess rule in case the server is using apache on a linux box.