Hide posts by banned users?

Hi,

A client of mine recently had me upgrade an older 1.2 site to 1.7. They are getting a ton of spam registrations, blog posts, and image uploads (via tidypics).

Client recently informed me that before the upgrade, when they banned a user, all their posts would disapper from the site (recent activity, etc.). Now the content remains when the user is banned. Is there anyway to hide all content from banned users? They do not want to delete, as that allows the spammer to re-sign up with the same email address.

TIA for any help or advice.