how to remove a user from my iMac with lion

In System Preferences > Users & Groups > click the padlock to unlock and authenticate > Highlight the user to be removed on the left > Click the "-" icon below the list.

Regards,

Captfred

Open System Preferences > Users & Groups.

Click lock icon and authenticate as administrator.

Select account to be deleted. Make sure it's the right one. You can't delete your admin account or the Guest account.

Click minus sign at bottom of user list. Confirm.