Long ago, I was running Movable Type with a link structure that looked like this:
http://www.bofe.org/archives/yyyy/mm/dd/entry-title
Then, I switched to wordpress which gives me this:
http://www.bofe.org/wp/yyyy/mm/dd/entry-title
Apache and mod_rewrite to the rescue.
Make a .htaccess file at the root level like this:
RewriteEngine On
ReWriteRule archives/(.*)/(.*)/(.*)/(.*) http://www.bofe.org/wp/$1/$2/$3/$4
Replace my domain with yours. Bliss!