Internal HDD doesn't show up in Windows suddenly. Was not having any issues a day ago. My OS and more crucial desktop files are on my SSD, so they are fine, but I have a couple hundred gigs of games, documents, photos, etc., on my HDD. I more or less have what I need off of it and expect I will have to replace it. Two questions:

1. Are there any other reasons beyond poor connection or failed/dead HDD that the drive would not show up on BIOS? It has my SSD displayed but empty for the other memory slot which I assume is where HDD once occupied.

I've gone through reset, updates to windows, the hardware scan on disc management, commend prompt troubleshooting (dskchk, sfc scannow), etc. Really most of the troubleshooting I have found online applies to the drive appearing on BIOS, and appearing on the disc management window when re-scanned, which is not the case for me. So is it basically just hardware issues at this point?

2. My most important files I placed on my C drive (SSD, with my OS), so I have many of them still. There's inevitably some things I haven't backed up from my HDD to an external, while not essential it would be nice to not re-download all these games and files again. What's a reliable process to retrieve this data from my current HDD, if I choose to replace my HDD? Or is retrieval method and viability dependent on why a disk failed?