Can't boot into hard drive

[M1N]

Hi. I was using a 1Tb hdd as my boot device in my PC for a long time. This was the only storage in the computer and it was working fine. I recently got a small 128gb SSD and put a fresh install of windows on it using a USB drive. I took the hdd out while I did this. I went into the bios and changed the boot order and it loaded into the SSD fine. I then reconnected the hard drive and booted into the SSD. The Hard drive showed up fine. I then changed the boot order and booted into the hard drive and it was fine as well. At this point I had two working copies of windows 10. Now, I have tried to boot into the hard drive again a week later and it doesn't work now. It says no bootable device OR goes into recovery mode. I can boot into the SSD fine but my hard drive shows up with no capacity value in file explorer and I can no longer access it. How can I fix this? I would like to boot into my hard drive normally again with everything still on it and remove the SSD for now as I would like to keep my progress if you will for the time being. Thank you, I would really appreciate the help.

[SpookyCitrus]

Maybe just coincidence but from how the drive is acting it sounds like it's died/failing. If it's an older drive with more than 1000 power on days I'd say it's probably time to just scrap it. 

[M1N]

3 hours ago, SpookyCitrus said:

Maybe just coincidence but from how the drive is acting it sounds like it's died/failing. If it's an older drive with more than 1000 power on days I'd say it's probably time to just scrap it. 

Yeah, I just think it's weird that it stopped working just after I had done all of this. It came up as being healthy in the disk management that day, and it is still saying that it is healthy and lists the partitions.

[Bipinvsnl]

Try changing the boot settings in bios to legacy instead of UEFI and then booting into the HDD