Watch the Five & Dime online guitar lesson by Brad Carlton from Chord Studies: Power Chords Vol. 1
This progression is based on the Em pentatonic scale, and we're just using power chords. Your index finger is going to do a barre on the second fret, fourth and fifth strings for the E5. Make sure on the G5 that you are muting the fifth string. To get the A5 drop your index finger down and you've got a great sounding progression.