Last year when we were applying SQL Server service packs across enterprise, on few of the instances during the Service Pack installation the following warning message was displayed.
The software you are about to install does not contain a Microsoft digital signature. Therefore, there is no guarantee that this software works correctly with Windows.
After clicking the Continue anyway button, this warning would disappear. But the Service Pack installation used to fail. This is because the Driver Signing Options are by default set to Warn - Prompt me each time to choose an action in Windows. To overcome this issue, the Driver Signing Options need to be set to Ignore. This option can be configured as seen below.
Windows Server 2003
Open System Properties and select Driver Signing.
Windows Server 2008
Open the Command Prompt as Administrator.
BCDEdit /Set LoadOptions DDISABLE_INTEGRITY_CHECKS
Using Local Group Policy Editor
This option can also be set using the Local Group Policy Editor and it is applicable to both Windows Server 2003 and 2008. Launch the Local Group Policy Editor by executing Run –> gpedit.msc. Then select Code signing for device drivers as seen in the below screenshot.
Using the methods explained above, the Unsigned driver installation warning can be disabled. After making this change, the SQL Server service pack completed successfully. Then the Driver Signing Options were brought back to the original state.