Try the following:
If that doesn't work try phone activation:
Windows FAQs and OEM Downloads
I'm getting the same error code, but I added Media Center to my Windows 8.1 PC and it changed to Windows 8.1 Pro with Media Center. What happens when I do that?
You will need to reinstall your original Windows 8.1 using a Windows 8.1 .iso. After that is activated you will then need to add the media centre key via add features. See here for details:
Windows FAQs and OEM Downloads
bro please help me same problem im having tell me how did u activated plzzz plz
Thanks @NATAKUC4! The Windows “9” Product Key Viewer from Softpedia worked for me.
I had a Lenovo ThinkPad Yoga I was restoring to factory settings when I got the 0xC004C003 activation error. The viewer has to be Run as Administrator, and if the key that is showing doesn't work (which did not for me, because it was the default key), then check the "MSDM Key" box and a different key will appear.
Thank you @ALMRLS after three days of getting nowhere with dell support and Microsoft... my product key was also the MSDM KEY!
Sir There are different factors that can affect for causing this error code: 0xC004C003
Most of the time this is caused due to invalid microsoft activation key, but you can solve this problem in different ways. You can learn more about this error from given link, They hav ectensively described about this windows activation problem.
<a href="masijee.com/error-code-0xc004c003">Error 0xC004C003</a>
I too had same problem and i called to dell support, they gave me wonderful answer that you are using a duplicate windows for 2 years after upgrading it is asking for verification.. we cannot do anything