windows 7 product key question?

[Invasion]

I have a n older sytem -dell- that came with windows 7. My question is.. if I get a new system can I install windows 7 with my dads windows 7 disc and use the product key from my older system.
So in other words will any windows 7 product key work on any windows 7 install disc.

Thanks

 

[Deception]

If its a OEM Copy (which I guess it will be if it came with the Dell), then it is attached to that system.

 

[Invasion]

Really. That is a shame so I have to buy a new copy
thanks for the info