Can I reinstall windows 8.1 using the same key used on my Hard Drive for my new SSD?

Solution
Yes, as long as the rest of the hardware is the same (especially the motherboard) it will activate just fine. When Windows activates, it makes a hash (unique identification number) based on the hardware it finds. This hash is sent to the activation server along with your product key. This is how MicroSoft tracks the activation of hardware to make sure that a product key isn't transferred to another PC (if it's OEM) or that it's not being used on more than one PC at a time.
Yes, as long as the rest of the hardware is the same (especially the motherboard) it will activate just fine. When Windows activates, it makes a hash (unique identification number) based on the hardware it finds. This hash is sent to the activation server along with your product key. This is how MicroSoft tracks the activation of hardware to make sure that a product key isn't transferred to another PC (if it's OEM) or that it's not being used on more than one PC at a time.
 
Solution