How do I figure out what size hard drive my laptop has? I've removed the hard drive and want to transfer files to new laptop. I need to purchase a SATA-to-USB cord kit and it says it has cords for 2.5", 3.5" or 5.25" hard drives. The hard drive is out of an HP Pavilion DV7 running windows 7 and is going to be plugged into an Acer running windows 7. Which hard drive do i have/which cord do I need?