Using a product key twice

[Jackriegerattack]

Im building a new computer for my grandpa because his hard drive died and his computer was very slow in general, im wondering what will happen if i buy the new parts and use his existing windows product key to save some money, or do i have to buy a whole new copy?

[Hans Christian | Teri]

Either it works, or you call Microsoft and they make it work for you.

[Br3tt96]

I've used my windows 7 product key 5 times overall. Worked every time.  Two different motherboards also

[Makarov_9mm]

I've used my windows 7 product key 5 times overall. Worked every time.  Two different motherboards also

Wow awesome! I'm saving one from a busted pc someone gave me for whenever I start a new build.

[simson0606]

it will work or you have to call microsoft (you will get one of those call menu things)

 

but if his old key is an oem key it is not legal to use them on another pc (the key will work fine, but it's not legal)

[LogicalDrm]

Should work. But it can be active on one machine at the time.