I am planning to upgrade my SO's 2009 MBP hard drive as it failed last week. I had an extra internal drive lying around from my old PC and I made it into a bootable Mavericks OS external drive using the directions posted here (https://support.apple.com/en-us/HT202796). I did not understand the last part of the article where it says "Once installation to your external device is complete, you can use it to start up your computer. You can then use Disk Utility, the Mac App Store and the OS X installer to install, or erase and install OS X on the normal startup drive of your computer" Can't I just pop this drive into the HDD slot and assume that this is the boot drive OR do I need to run some commands to let OS know that is a primary boot drive now? Also, I plan to upgrade the MBP to a new SSD. How do I make the transfer in the easiest possible way? Sorry if I have asked stupid questions but I haven't dealt much with Mac OS and not sure how to install the OS from an external boot drive.