The private pilot reported that he left the windows open while completing the start-up checklist and while taxiing to the runway. During the takeoff roll, he noticed the passenger window was unsecured. In his attempt to secure the window, he momentarily took his eyes off the runway. As he looked back, the airplane was traveling to the left side of the runway. With insufficient room to correct direction, the airplane collided with a runway distance marker sign.

The airplane sustained substantial damage to the right horizontal stabilizer and elevator.

The pilot reported that there were no mechanical failures or malfunctions with the airplane that would have precluded normal operation.