I recently met (and am considering working with) a guy who does credit restoration. They have a patented process that is even able to remove valid negative items from credit reports. It's based on a loophole in the Fair Credit Reporting Act.
It takes some time, but based on the evidence he's presented is really seems to work. I've seen many letters from the credit reporting companies listing negative items that have been removed. $600 is a lot of money, but if you get a lower interest rate on the mortgage, car loans, and credit cards it wouldn't take long to recoup that.
http://www.TheFulfillmentCenter.us