Question
I have a newly hydro seeded lawn that was started on the 7 SEPT 2007 which type of fertilizer should I use.

Answer
Assuming you are in Cool Season Grass country, and it is now mid-October, and your Soil is in excellent condition, you would top dress with a high organic content product like aged Manure, Bloodmeal, etc.  In the Spring, the Soil will generate enough Nitrogen for Grass Green-up to power a Space Shuttle to Mars, at a constant rate corresponding with the Soil and air Temperatures.

Don't panic if your Lawn seems to be taking a while.  It is late to be doing this.  Spring will give you something to celebrate.