This little website has been online since 1998 (back in the embarrassing days of terrible bedroom derived HTML layouts) and running Drupal since Spring 2007. Over the course of the last four years of drupalishness, the online world has been attacked by spammers - the web equivalents of junk mailers. 

I was just upgrading a few modules, tidying and demoting some old content and found hundreds of registered users that have never ever been logged on. So, it;s time for housekeeping and delete that stuff to trim it down.

Bring on the User Prune module - http://drupal.org/project/user_prune

Very cool and once uploaded, installed in ../sites/all/modules just enable it:

and then go run it http://www.projex.com/admin/user/prune (obviously you would put your domain name in place of projex :/ duh! )

It's a very cool utility and neatly removed just over 90 duff user accounts: