how do i completely delete my iCloud account?

You can't delete it from the server. You can sign out of it in System Preferences (or Settings)>iCloud, and if necessary go to http://www.icloud.com and manually remove any data you don't want to be there.

Could you bring your signature up to date so that when you ask a question we know what you're using. If you're using iCloud your not running 10.5.1 or a G5.