Like someone else the pegs were too short and thus the window would not stay in the track.  It turns out the pegs fit very tightly and can be adjusted out using a pliers.  Regarding getting the window  in the track- There are 4 plastic stops and one magnetic stop.  They are easy to remove with a phillips screw driver.  Holding the window up and down you  slide either peg along the track to the back corner--now the other peg should  clear the front molding.  Holding the window in the up position,   reinstall the plastic stops.  If you pull the pegs out too far you might have to tap them in until the window fits and slides. I'm a 68 year old female and I could do it.  (note: be sure and install the knob correctly  before installing the window- it comes reversed for shipping)

Pros: Really nice looking for the money
Cons: Peg problem