HP Pavilions 6644D’s won’t start

My company offered employees the chance to purchase HP Pavilion 6644D’s through an employee purchase program. I have had several co-workers including myself who report that the power switch fails to work on these computers. When you press the power switch nothing happens. No power. Sadly, the computers are no longer under warranty. Before I start yanking out power supplies, is there a better way to troubleshoot this problem.