Working SSD in New System Won't Boot

[nttom]

I moved a working SSD that has windows 10 on it to a new computer build. I upgraded from a Alienware X51 from ~2013 to a brand new system (by this I mean it is different used components) but now upon start up it reads: "Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key" I know the SSD is a working seeing as I just pulled it out of another build. I also am sure the power cord as well as the SATA connector are functioning. The motherboard I'm trying to connect to is the MSI B150 PC Mate.

 

[rgd1101]

Was there a HDD in the X51?

 

[nttom]

Was there a HDD in the X51?

I got rid of the HDD from the X51 and replaced it with an SSD about a year ago. I pulled the SSD out of that rig and placed it in my new build but it won't boot.