I have a Samsung np550p5c-s05in and it came installed with Windows 8 64-bit, later the hdd developed some problems and as I had warranty , they replaced it with a new one however this one came with a Win 8 32-bit which was not activated. Now , I had the product key from last win 8 that I had so I tried using that to activate but an error came up which said something like "The key provided is not for this edition of windows , Either use the windows 8 setup or enter a windows 8 activation key." So this made sense as the key I had was for a 64 bit win 8 , so I installed win 8 64-bit from an image file and then I repeated the same procedure of entering the key and the same error came up again. So I would request you people to please help me with this, as I have no idea whatsoever what to do next.

Try activating Windows 8 by phone

Press Windows key + x then click Run, then type: slui.exe 4 (Alternate method: Press Windows key + r then type: slui.exe 4)

Next press the 'ENTER' key.
Select your 'Country' from the list.
Choose the 'Phone Activation' option.
Stay on the phone *** do not select/press any options *** and wait for a person to help you.
Explain your problem clearly to the support person.
Microsoft Support - U.S.
http://support.microsoft.com/contactus/?pid=17655&tid=100109454
Microsoft Support - UK
http://support.microsoft.com/contactus/?ln=en-gb
How and when to contact Microsoft Customer Service and Support: http://support.microsoft.com/kb/295539 Explain your problem clearly to the support person and they will transfer you to the activation department

How to contact a Microsoft Product Activation Center by telephone:
http://support.microsoft.com/kb/950929