Should I install and create a windows 10 CD (from Win7) before I buy a new Z170 system or after?

[WPCentral Question]

My system is 5 years old running Win7 and I'm planning on buying a new system within the next 6 months, my worry is if I install Win10 on my current 5 year old system it will tie itself to this hardware. If I then in 6 months time buy and build a rig will I be able to use the same Win10 key for it, or will it say no deal and force me off to the shops to pay for a new copy? Any help is much appreciated cheers