How to boot up second HD?

My laptop (I7 8550U) has space for 2 hard drives. Primary drive has WIN 10 Secondary drive has WIN 7. I want to boot up this HD. I have tried the BIOS menu screen (via: Settings > Recovery > Restart > Troubleshooting). But in the BIOS Boot menu there is no option to boot the second HD because it... show more My laptop (I7 8550U) has space for 2 hard drives.
Primary drive has WIN 10
Secondary drive has WIN 7. I want to boot up this HD.

I have tried the BIOS menu screen (via: Settings > Recovery > Restart > Troubleshooting).
But in the BIOS Boot menu there is no option to boot the second HD because it doesn't recognize it as a distinct device.
It treats the partitions of the second HD as an extension of the primary HD.

Solutions?
3 answers 3