I have a windows 2008 r2 enterprise server and It says that this edition is not valid. How do iregistor that

OK I am working on a windows 2008 r2 core server. And it says that the edition is not a valid copy.
how do I make it valid and where do I put the numbers in that I have to make it valid.
remember that this only seems to have a comand prompt no real GUI, so that is why I am confused
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Try running

slmgr.vbs /?

from the command prompt.

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Darius GhassemCommented:
explorer648Author Commented:
I left the customers site hoping never again to touch a core 2008 server. Ever again. Ever again Ever again Ever again Ever again. Ever again Ever again Ever again Ever again. Ever again Ever again Ever again Ever again. Ever again Ever again Ever again worst product microsft has ever come out with ever. too hard to do anything in.
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Windows Server 2008

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