0xC004F038: The returned count from your Key Management Service is insufficient

by Shijaz Abdulla on 02.11.2008 at 10:19

We have a KMS Server that has been activating Vista clients for several months. A few days ago our desktop team came across the following Windows Activation error on one of the Vista Enterprise machines:


Error 0xC004F038 The computer could not be activated. The returned count from your Key Management Service is insufficient.

The KB Article 942961, which describes this error message, did not apply to us, because our KMS count is more than 25 and the article suggests that this problem only happens when the count is lesser than 25.

We resolved the issue by re-arming the Windows Activation on the client machine and then trying to do an automatic activation after a restart. Here’s how we did it:

  • On the offending Vista Enterprise client, type:
    slmgr.vbs -rearm
  • After a restart, type the following command on the same machine:
    slmgr.vbs -ato

The -rearm switch "re-arms" or "resets" the Windows Activation on the client machine. This can be done a maximum of three times per Windows Vista installation. The re-arming also extends the grace period, so it is particularly useful if you are looking for a temporary fix to buy some time while you sort out KMS issues.

Getting KMS to activate Windows Vista and Windows Server 2008

by Shijaz Abdulla on 21.07.2008 at 21:31

Starting with Windows Vista, Volume License Keys (VLKs) have been replaced by the Key Management Service (KMS). A KMS Server is deployed in the organization, which will respond to activation requests from client machines. Hosts activated via a KMS have to report back to that KMS key server once every 180 days.

At the place where I work, a Key Management Server was already in place and it was used for activating Windows Vista. With release of Windows Server 2008 earlier this year, we started deploying/migrating some of the workloads to the new server OS.

Windows Server 2008 also uses the KMS activation system. However, the KMS server refused to activate Windows Server 2008 computers, while Vista was OK. Upon closer examination and long discussions with Microsoft, it was discovered that the KMS key installed on our KMS server was only for Windows Vista. Microsoft calls this a "Class A" key.

In order for the KMS server to be able to activate BOTH Windows Server 2008 AND Windows Vista, we should remove the "Class A" key, replace it with a "Class B" key and then activate the KMS server. Here, the "Class B" key is nothing but the Windows Server 2008 Std/Ent – KMS key on the MVLS website. This key can not only activate WS08, it can also activate Vista!

This is how its done (from the Command Prompt):

slmgr -upk
uninstalls our "Class A" KMS key.

slmgr -ipk <insert Windows 2008 KMS key here>
installs the "Class B" KMS key.

slmgr -ato
activates the KMS server

While using slmgr, it is important to wait 5-10 seconds after each command to get the confirmation popup box, even though command prompt will return as though nothing happened.

Once the server has successfully activated, type the following command to verify that you have a "Class B" KMS key.

slmgr -dlv

kms dlv
Notice that it says KMS_B channel, indicating a "Class B" KMS key that will activate both Windows Server 2008 and Windows Vista.