Stop reseating RAM before you check the power supply button on the back of the case
I had a tower come in Tuesday from a guy in Fresno who swore his RAM died after a power flicker, and he had already pulled and reseated both sticks twice. Before I opened the side panel I flipped the rocker switch on the back of his PSU, which was sitting in the off position, and the machine posted on the first press. He had bumped it while sliding the tower out to vacuum behind his desk, and spent two hours chasing dead memory for nothing. I have seen this same thing four times since March, and every time the customer insists it cannot be the switch because "it was working fine yesterday." Ask them to check the back of the case and the wall outlet before they touch anything inside, and save yourself the bench time. What is your first no-tools check when a machine will not post?
Are you sure that switch was really the fix though, or did reseating the RAM just need one more power cycle to finally take? Plenty of times the board just needed a full drain and that back switch is a coincidence you're crediting.