Kris wants to get a new hard drive for his Mac. Leo says to get a 512GB hard drive that will house the OS and programs, and then an external drive for data. Going with a Thunderbolt 3 will make it faster than the internal drive.
Scott wants to know if he can take the hard drive out of an old computer and then put it into a new one. Leo says yes, but he should only use it as a data drive. He could probably put it in an external USB enclosure so he can plug it in when he needs to. He could install it as a secondary hard drive as well. If he wants to use software from that hard drive, that's a lot more problematic due to registry issues. He may be able to dual boot from the older driver, but the device drivers won't work. So he'll have to work around that and use a boot manager.
Ziggy is a high school senior and he's taking classes in video game design. He wants to have a really good SSD to speed up the performance of his computers. Leo says that's a great idea and it's important to find an SSD that's really fast as some aren't as fast as others.