Here's how to do it: 1. Open the Run Menu (Windows Key + R) 2. Type regedit (Opens Registry Editor) 3. Navigate to HKEY_Local_Machine (In left pane). 4. Open the folder and navigate to Software. 5. Go to Microsoft. 6. Then go to Windows NT. 7. Open Current Version. 8. In the right pane you should see EditionID. 7. Double Click That and type "Professional" (Without quotations). 8.Insert Your Windows 8 Pro DVD or Flash Drive in PC and Upgrade It. I made a similar post about removing WMC from Windows 8 to Activate it. Just Do the Same thing here as listed above.
To be clear: Product keys are SKU specific. For Pro, you need a Pro key, an Enterprise N one won't work for Pro.