Now that we are all able to check our credit reports yearly for free, I have to take a moment to urge everyone to do just that. At the beginning of the summer, I pulled mine, and one of the bureaus was showing two accounts at collections that appeared to stem from a hospital stay in West Virginia in 2006. Now, I haven't lived full time in WV in over 12 years, and knew I hadn't been seen at this particular hospital since childhood. A few phone calls revealed that a patient with my same first and last name, but totally different address, date of birth, and middle initial had inadvertantly been "Attached" to my social security number when he checked in. A somewhat understandable, and I imagine, common, mistake.
However, it was quite difficult to actually get the items removed. The first account was removed easily enough, but the hospital had actually outsourced their patient billing in the year between this other "me" being admitted and the time the real me found out about the accounts. This meant several months of phone calls, speaking to "higher ups" and an eventual phone call to the director of the hospital. I was told by no less than six people that the problem had been corrected, only to pull my credit and find that it was still there. Turns out, they had fixed the issue in their system but never bothered to notify the collections agency.
A pain in the butt, but worth it to clean it up. Im not sure how many "points" a collections account knocks off your score, but I purchased a car during the week that these were finally removed, and getting them off of there raised my score enough to qualify for a more preferred rate (two percent lower). On a thirty thousand dollar car loan, that meant almost fifty bucks a month I saved.
So, my advice, is to check it every year and vigorously work to remove any mistakes that are there. It could mean a big difference the next time you buy a home or car.