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Windows Server 2003
Open System Properties and select Driver Signing.
In the Options screen select Ignore.
This change will come into force without rebooting the server.
Windows Server 2008
Open the Command Prompt as Administrator.
In the Command Prompt enter the following command.
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.
In the Properties screen, select Ignore.
Using the methods explained above, the Unsigned driver installation warning can be disabled. After making this change, the unsigned driver can be installed successfully. Then the Driver Signing Options can then be brought back to the original state.