I used this exact technique to clean up my own credit. Starting a year and a half ago, I've had about a dozen collections and negative accounts removed from all three credit bureaus doing EXACTLY what you describe here. I only have on negative account left, and they've never indicated the account is disputed on my credit reports, or sent me proof the account is mine, despite me sending the round of letters twice. I'm going to have to take that one to small claims court. But, all the others were removed with these letters, even if I DID have to send some of them more than once. I've also improved my credit even more by qualifying for new credit cards (and keeping the balance low), being added as an authorized user on other ones (to age my credit), getting old addresses removed, and getting inquiries removed. It DOES work.