Same account, multiple derogatories

First, I'd just like to introduce myself and say how happy I am to have found this resource! I'm now 31, and have been living a mostly cash based life since I destroyed my credit back in college. I'm finally sick of it, and have decided to get serious about getting my financial life back on track. It's wonderful to have a forum where one can find real world advice and (perhaps more importantly) moral support from other people who have been where I am. It's also nice to get advice from people who realize that the answer is more complex than simply "pay the bills off".

OK, on to my question, which I'm sure will be the first of many:

I just got a copy of my credit report last night, the "3-in-1" from consumerinfo.com. Holy Cow! Not as bad as I thought! OK, sure, my scores are complete crap (514, 568, and 553), but the number of items on there isn't nearly as bad as I had feared. I can handle this!

Here's the thing. Several bad accounts appear multiple times. Once for the original creditor, once for a collection agency, and one even for another collection agency.

What is the best way to go about getting rid of the multiple entries? I don't want to send $1500 to three separate places to clear up a single $1500 account. I'm not at all opposed to paying the money that I owe, but I don't want to pay it multiple times.

Should I negotiate with one creditor, then dispute the rest? Or dispute them all and negotiate with whoever still remains? Or is there a better way to handle this that I'm not considering?

Also, am I correct in my assumption that my credit score is worse than what it really should be, since what appears to be 2, 3, or even 4 bad accounts is, in reality, just one account?

Thanks for your help (and sorry for the length of the post)