Midland Credit again.....

I have posted on here before about Midland Credit but they are at it again. I have old credit card debt (around 2000 and before) fron Capital One and Providian. Both were bought by Midland in early 2001. The original creditors have been removed from my credit report but Midland has not. They do not call me, mail me, or any real attempt to collect the debt because they know by now they can't but they constantly post on my credit report. Over the past 3 years I have disputed every Midland account, over time they were removed, then readded with a different date, removed again, added again with different date and amount, finally removed again two months ago. Then last month they added a new account number with an old amount, now this month they listed again with an old amount but new account number and date. This only happens with Experian. How can this be legal? How can I stop them from continuing their listings with wrong info and get off for good? Even in their letters (in 2001) they refused to give proper information. My last validation letter to them was returned with a "legal document" filled out with my answers as if to say that I was being sued. I had another creditor try to sue me by doing that and I didn't fall for it then either. Has anyone ever been able to get Midland to leave them alone?