Windows 10: Reuse Windows 10 Activation Key on the Same PC

The Windows 10 activation key is still valid on my PC and I want to reinstall the Windows 10. Can I still use that activation key ?

:)

 

windows 7 key reuse

I'm asking the second thing, if I can reuse my windows 7 key on another machine without any problems. (sorry, I see I forgot to mention it in the original post ^^)

 

windows 7 key reuse

Hey guys,

I'm selling my 1 year old laptop (laptop 2 in sig), which came with Vista OEM.
I installed windows 7 on it with a key from MSDN. My best friend(the buyer) will format the laptop before he gives it to his sister, so I wanted to know how I can reuse my key for a new pc in the future.

I googled a little bit, but I couldn't find a clear answer. Will I have to call Microsoft or something?

kind regards,