Slander is being spread by my ex employer that I was fired, but I had put in a 2 weeks notice. What do I do?

I recently put a 2 weeks notice in and was asked to leave the day I placed my notice. Within 45 mins. of me being told to leave I am hit with gossip that I was fired because of conversations I had had with HR. I had yet to tell a soul due to the fact I was busy packing. The news had even spread in less that an hour to another building 40 miles away. I was recently asked by a potential employer who was considering me for a managers position of why I was fired. I had to set the story sraight and he told me that that's what he had heard. I am still on payroll until the 16th of July and I have asked HR to help with this. They told me there was nothing they could do about it. I asked HR for EEO's number and what the Department of Labor could do and was told by HR that neither could help me. Unfortunalty I have been told that this is common behavior for this company. What can I do to protect myself?