I was doing a clean install of windows 10 on my computer to overwrite the old version that I no longer have a key for. Unfortunately, when I went to select what storage device I wanted it installed on, neither of my 2 SSDs qualified because they were not GPT disks. I stupidly thought that hitting reformat on my dedicated OS SSD would fix the problem but now it has just disappeared from the list of options and I can't even install the device on my main 2 TB SSD.

Am I screwed? Do I need to buy a new SSD? How do I get Windows to install? How can I get my OS SSD to show back up as an option?