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Activation error What it means and how to fix it
   
Unable to activate Windows 8 Pro with Media Center. (Error code: 0xC004C4AA) You might see this error after you used the Add Features to Windows 8 app to upgrade your current edition of Windows. The Windows 8 Pro with Media Center edition can only be activated on PCs that had Windows preinstalled, or Windows was purchased on the Windows website or at a retail store. To fix the problem, you need to install Windows with the product key provided to you in an email or with the DVD. If you think you have received this message in error, contact a Microsoft Customer Support representative.
   
Genuine Validation detected tampered Windows binaries. (Error code 0xC004C4AE) You might see this error if you used a third party app to add a display language that isn't currently supported by Windows to your PC. To fix the problem, you can reset your PC to undo the changes that were made to Windows. See How to restore, refresh, or reset your PC for more info.
   
A networking problem has occurred while activating your copy of Windows. (Error code 0xC004FC03) You might see this error if your firewall settings are preventing Windows from completing the activation process online. To fix the problem, you can activate Windows by phone instead.
1. Swipe in from the right edge of the screen, and then tap Search.
     (If you're using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, and then click Search.)
2. Enter SLUI 04 in the search box, tap or click Apps, and then tap or click SLUI 04.
3. Follow the instructions on the screen.
   
The activation server reported that the Multiple Activation Key has exceeded its limit. (Error code 0xC004C020) This error occurs when a Volume License (a license that has been bought from Microsoft by a business to install Windows on multiple PCs) has been used on more PCs than the Microsoft Software License Terms allow. To fix the problem, you might need to use a different product key to activate your PC. Contact your system administrator for more info.
   
DNS name does not exist. (Error code 0x8007232B) You might see this error if you're trying to activate your work PC but aren't connected to your workplace's network. If you're connected to your work network and still see this error, you might need to change your network settings. Contact your system administrator for more info.
   
The filename, directory name, or volume label syntax is incorrect. (Error code 0x8007007B) You might need to enter your product key again. To fix the problem, follow these steps:

1. Swipe in from the right edge of the screen, and then tap Search.
     (If you're using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, and then click Search.)
2. Enter SLUI 03 in the search box, tap or click Apps, and then tap or click SLUI 03.
3. Enter your 25–digit product key and tap or click Activate. Administrator permission required You might be asked for an admin password or to confirm your choice.

Note:
You can find your product key on the box that the Windows DVD came in—or in an email that shows that you bought Windows. It looks like this: PRODUCT KEY: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX 
   
A security error occurred. (Error code 0x80072F8F) Windows is having trouble connecting to the online activation service and couldn't verify your product key. Try activating again later.
   
Unspecified error. (Error code 0x80004005) If you see this error, try activating again. If that doesn't work, you might need to reset your PC. See How to restore, refresh, or reset your PC for more info.
   
You upgraded to Windows 8, but didn't have a previous version or the correct edition of Windows installed (error 0xC004F061) If you see error 0xC004F061 when you try to activate Windows 8, it means one of the following:

> You're using a product key to upgrade to Windows 8, but a previous version of Windows wasn't on your PC. To upgrade to Windows 8, you need to have Windows 7, Windows Vista, or Windows XP already installed on your PC.
> If you formatted or replaced your hard drive, you won't be able to use a product key to upgrade to Windows 8. You'll need to install your previous version of Windows, and then reinstall Windows 8.
> You’re trying to install the Windows 8 Pro Pack, but you already have Windows 8 Pro installed on your PC. To upgrade your edition, you’ll need to install the Windows 8 Media Center Pack instead.
> You’re trying to install the Windows 8 Media Center Pack, but your PC isn’t running Windows 8 Pro. To upgrade your edition, you’ll need to install the Windows 8 Pro Pack first.

Troubleshooting Steps:
1. Open regedit (should Run as Administrator) > HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionSetupOOBE << this is in the navigation pane (left side)
2. Change the value of MediaBootInstall to 0 << Right click, then Modify and then close regedit
3. Open elevated command prompt (run as Administrator) > slmgr.vbs -rearm
4. Restart computer and then manually activate windows again.
Note:
If slui is not working >(In elevated command prompt) slmgr.vbs -ipk "put the product key here WITH dashes" then slmgr.vbs -ato 
   
One copy of Windows might have been installed on multiple PCs (error 0xC004C008) If you have one copy of Windows and installed it on more than one PC, activation might not work because the product key has already been used on another PC, or it's being used on more PCs than the Microsoft Software License Terms allow. Normally, the rule to follow for most copies of Windows is 1:1, meaning that one copy of Windows can be installed only on one PC.

If your product key is being used on more PCs than the Microsoft Software License Terms allow, you'll need to buy a product key for each one of your PCs in order to activate them.
http://windows.microsoft.com/en-us/windows7/windows-7-activation-error-0xc004c008
How to contact a Microsoft Product Activation Center: http://support.microsoft.com/default.aspx/kb/950929/en=us