What is critical to know about memory installation procedures on the HP ProBook 640 G2?

When installing a new memory module: First power off laptop completely and disconnect all peripherals plus unplugged power cables. Sequentially remove components starting with service door, battery, SSD/HDD drives, WLAN/WWAN modules then optical drive before reaching memory bay area. Place new RAM units ensuring notched edge aligns properly with the slot tab; gently tilt module upwards at around 45 degrees and press into place until retention clips engage snugly holding in position. (Page 50)