I have a 2004 Chevrolet Silverado 5.3 V-8 with 121,768 miles.

Now the long and short of the problem I am having is the battery went dead and now it won't start.I can hear the fuel pump running it has a 1/2 of a tank of gas and the battery tested good.Now what I have tried so far is take the battery cables off and hold them together for 30 seconds to reset the computer but to no avail.Does anyone have any suggestions I am out of ideas and almost at the end of my rope. Thanks