How long do creditors have to report delinquencies?

I had a residential apt building and all the electric bills were seperate for each unit. I sold the building at the beginning of the year. Now 6 months later the electric company has sent several delinquencies to my credit report from 2004, 2007, 2008, and 2009!!! I didn't even know they existed!! I can't go back that far on my bank records to see if they were paid. How do I get these off my credit report!? Please help!