Você não pode usar todos os drivers do Windows 7 no Windows Server 2008 R2. Os drivers devem ser assinados.
On all x64 versions of Windows, drivers have to be digitally signed. I guess the logic behind this is for reasons and stability and compatibility. You could however, still force an install of a non-signed driver. The result however, could be some annoyance.
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To get around this, driver signature enforcement would have be disabled at each start up. The way this is done is to hit F5 right after the BIOS POST screen and before Windows start, and then hit F8 to bring up the advance options, and select disable driver signature enforcement. Troublesome.