I have added two portal user. Now I want to delete these users (setup->customer portal->users), but I can only activate, deactivate and re-invite user.

Before adding these users in customer portal, I have added them in contacts and after that I have deleted them.

I  have added theses two user with my 2 different email id. The reason behind is before going live I wanted to test my invitation mail, how its looks in template and its embedded link to accept the invitation, whether acceptance link is working fine or not etc.

I am also attaching an image of the setup->customer portal->users screen as well.