There are a few things you need to take into account when dealing with accounts gone to collections. ( this is coming from someone who has had multiple dealings with collections)
1. Ignoring it will not make them go away, even if they fall off your credit report. If they still fall within your state's Statute of limitations they can still go after you.
2. How much is the debt for?
3. With the new changes in the bankruptcy laws, Collection Agencies and Credit card companies are sueing at a much higher rate.
.4. Pay for deletions are possible, you may have to work hard on it but they are obtainable. I for one had no luck what so ever in obtaining them, but some have, so it is without a doubt worth a shot.
I personally reccomend not fooling around with them. Again try to get a settlement or a good payment plan. If you don't think these guys won't come after you just read some post on this forum
http://forum.freeadvice.com/forumdisplay.php?f=84 these are real life horror stories of what Collection Agencies can do to you. Not only will a judgment destroy your credit report, that will be the least of your worries when they can put a lien on your house or they seize your bank account.
I'm not trying to scare you into doing anything, I just think you need to know what could be some of the consequences by ignoring them.
Try Debt validating them,
Figure out your date of first delinquency and see if they are passed your state's Statute of Limitations
I also subscribe to the belief that before you work on your credit score you need to clean up all the baddies first. You can dillute your score all you want by opening up new credit cards and such and being good on them but while the collections and chargeoffs still remain unresolved that bump in score means nothing in a manual review of your score. besides you have a house and a car ( I assume) those are the real reasons you want a strong FICO SCORE and since you already have them, I would say go back and clean up the debt.