Hello, you fine people of MacRumors. I am way behind the times, running OS Lion 10.7.5 on a 17" Macbook Pro. I need to upgrade my OS and my external hard drive is out of space. No problem, right? Just buy a new hard drive. Unfortunately, all the drives in my local store are compatible with Sierra, El Capitan, and above. I bought a drive, and did the erasing and partitioning as in times past, but my computer and Time Machine still won't recognize it. My question is, what drive can I buy in 2017 that's not an expensive Time Capsule (more than $200USD used). Because I need to backup before I can install a new OS and do it relatively inexpensively. Thanks!