Need help from technical folks (Windows/PC Hardware content)

So I decided to upgrade my music dekstop by adding a SSD. The SSD cloning went fine. I wanted to keep both the SSD and HDD (for additional space) but when I booted my PC it didn't give me a boot option and booted with the HDD as default. There is no UEFI option as the BIOS is legacy. I disconnected the HDD and it picked up the SSD by default upon boot. However, now when I re-connected the HDD, it doesn't show that in My PC or Disk Management at all. I disconnected the SSD and then it picks up the HDD by default. So it seems like I can only connect 1 of the 2 but ideally I want to format the HDD and use that for storage so want to use the SSD to boot but also show me the HDD so that I can format it. It's not a cable issue as individually both drives work fine when connected to their respective cable. Hopefully it's not too confusing and makes sense. I am on Windows 10. Thanks!

Did you change the boot order in the BIOS?

See if you can download a manual for your motherboard - there might be a jumper you can remove to access the bios - I just went through this on someone else's pc last week, and it fixed it.

I figured it out. I was using the HDMI cable and for some reason the monitor doesn't turn on until the Windows login screen shows up. I switched that out with VGA and I was able to get the POST screen and access BIOS. Thanks everyone for the help!

Congrats! Good job.