Here's the balanced equation:

C3H5(NO3)3(g) → 3CO2(g) + 2.5H2O(g) + 1.5N2(g) + 0.25O2(g)

Why is it so violently reactive?

Here is the explanation:
http://antoine.frostburg.edu/chem/senese/101/redox/faq/nitroglycerin.shtml

That was exactly what I needed, thanks.

You are welcome! http://jackson8.com/images/amhd/thumb.gif