Symptoms :

On already activated KMS client a Windows Activation window comes up with the error

An error has occurred:

Code: 0xC004D302

Description: The Security processor reported that the trusted data store was rearmed.

Cause :

1. Changes in the default permissions of the "C:\ProgramData\Microsoft\Crypto\RSA\MachineKeys" .

2. Corruption in the Licensing Files.  (tokens.dat)

3. If you have run the slmgr.vbs /rearm command and try to run any other activation command(/dlv or /dli for example) prior to rebooting you will experience this error.  You must reboot after using the slmgr.vbs /rearm command prior to attempting activation.

Resolution:

1. Change the directory on the command prompt by typing in

(For Vista and Windows 2008)

cd "%windir%\ServiceProfiles\NetworkService\AppData\Roaming\Microsoft\SoftwareLicensing"

(For Win 7 and Windows 2008 R2)

cd "%windir%\ServiceProfiles\NetworkService\AppData\Roaming\Microsoft\SoftwareProtectionPlatform"

2. Backupy tokens.dat to tokens.old  by typing the command and copy the token.dat from activated machine.

ren tokens.dat tokens.old

3. Activated using slmgr command by typing in

- slmgr –ato  (using Internet)

- slui.exe -4  (using telephone)