To install unsigned drivers on Windows Server 2012, you have to disable the Digital Signature Driver Verification.
In previous versions (before 2008 R2 or something like that), you could simply disable the check through group policies in gpedit.msc (User Configuration-> Administrative Templates-> System-> Driver Installation, Code Signing for Device Drivers). Now the rigid concept of security is replaced by the brutal arbitrariness of Microsoft. Fortunately, they still left a loophole.
Run the command line with elevated privileges and execute the following commands in sequence:
Bcdedit.exe /set nointegritychecks ON
Bcdedit.exe /set TESTSIGNING ON
After each command, a success message should appear: Instead of the first of these commands, you can do:
bcdedit.exe /set loadoptions DDISABLE_INTEGRITY_CHECKS
Return to normal:
Bcdedit.exe /set nointegritychecks OFF
bcdedit.exe /set TESTSIGNING OFF
Or instead of the first:
bcdedit -set loadoptions ENABLE_INTEGRITY_CHECKS
After you run these commands, you must restart the server.
Now in the lower right corner there will be an inscription stating that Windows Server 2012 is running in test mode. You can get rid of the inscription, but it makes no sense. So immediately you can see that everything turned out and the test mode is enabled.
Remarks:
1. On the account of the first lines I am not sure, but “bcdedit.exe / set TESTSIGNING ON” is mandatory.
2. Instead of these manipulations, you can boot into F8 in a special mode, ignoring unsigned drivers and installing an unsigned driver, but after rebooting the server, this driver will not work.