As far as your credit scores are concerned it makes no difference if you pay off that old account in full or reach a partial settlement. That's why you may want to at least try to get the collector to agree to remove the account if you pay it.
Also keep in mind that a settlement does not affect how long the account will remain on your credit report. It's still 7.5 years from the date you first fell behind.
We will be posting a new (free) podcast about getting collection accounts off your credit reports here soon. Be sure to subscribe to our ezine so you'll get the notice when it is available.