Client machines may fail to boot into PXE if System Center Configuration Manager Service Pack 2 has been applied


Consider the following scenario:

  • An operating system is deployed to a client computer in a System Center Configuration Manager 2007 Service Pack 2 (SP2) environment.
  • You try to deploy another operating system to the same client within one hour of the previous deployment.

In this scenario, the deployment process fails. On the client side, the computer tries to restart from the local hard disk instead of from the Pre-Boot Execution Environment (PXE) image.

Additionally, the following message may be logged in smspxe.log:

Loaded PXE settings from reg key HKLM\Software\Microsoft\SMS\PXE:
PXE Settings:
    IsActive: Yes
    SupportUnknownMachines: No
    MACIgnoreListFile: <empty>
    ResponseDelay: 0
    CacheExpire: 3600
    HTTP Port: 80
    HTTPS Port: 443
    IISSSLState: 0x0
    BindPolicy: Exclude <empty>
    TRK: <non empty>
    SiteSignCert: <empty>
    Root CA Certs: <empty>
    PXE GUID: fab8bfcc-3b15-431a-828d-fbfd184c3813
    PXEPassword: <empty>


This problem occurs because of a PXE cache limitation (of 1 hour) if System Center Configuration Manager 2007 Service Pack 1 (SP1) has been upgraded to SP2 after the hotfix that is described in KB 969113 has been applied in a Configuration Manager 2007 SP1 environment.


Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 How to back up and restore the registry in Windows

To resolve this cache limitation, you must change a registry value on the computer on which the ConfigMgr PXE service point role is installed. To do this, follow these steps:

  1. Click Start, type regedit in the Start Search box, and then click regedit in the Programs list.

    Note If you are prompted for an administrator password or for confirmation, type the password or provide confirmation.
  2. Locate and then select the following registry subkey:


  3. Right-click CacheExpire, and then click Modify.

  4. Configure the cache expire value. For example, set the value to 120 seconds (two minutes). To do this, follow these steps:

    1. In the Value data box, type 120.
    2. In the Base area, click decimal.
    3. Click OK.
  5. Exit Registry Editor.
  6. Restart the Windows Deployment Services Server service. 

More Information

  • Microsoft System Center Configuration Manager 2007 Service Pack 2