Email the ed using the contact us at the bottom of the page and they might delete it. though what's the problem with just leaving it, the idea of this site is to be a bank of answers.
It depends on why you can't use it. If it's an old one that has not been used-it may no longer be active. If the user has been suspended-then it will become active again in a week or so. To have a second account means running the risk of being suspended again, or of being banned.