Using an online software in 2007 (last year) I came to the dependents section. I am positive it said "under 18 by year end 2007 or under 24 if full-time student for at least 5 months of year."
My daughter was 18 in November 07, graduated High School but only spent 10 weeks as full-time college student.
I don't think I qualified her as a dependent and may have missed out on a deduction.
This year it says "under 19 by year-end".

If I missed out a dependent deduction last year can I go back reclaim back taxes from last years Tax return from the IRS?

The age requirement for a dependent child is she must be under age 19 at the end of the year, or under age 24 at the end of the year and a full time student.

Yes, you can file an amended tax return for 2007 (form 1040-X) and you should get some money back.