When you connect a new hardware device to your computer, Windows tries to find and install a software driver for the device. Occasionally, you might see a notification that a driver is unsigned, has been altered since it was signed, or can't be installed by Windows. You can always decide whether to install a driver that's unsigned or has been altered.
A signed driver is a device driver that includes a digital signature. A digital signature is an electronic security mark that can indicate the publisher of the software, as well as whether someone has tampered with the driver since it was signed. If a driver has been signed by a publisher that has verified its identity with a certification authority, you can be confident that the driver comes from that publisher and hasn't been altered.
Windows will alert you with one of the following messages if a driver is unsigned, was signed by a publisher that hasn't verified its identity with a certification authority, or has been altered since it was signed and released:
The driver either doesn't have a digital signature or has been signed with a digital signature that wasn't verified by a certification authority. You should only install this driver if you received it from an original manufacturer's disc or from your system administrator.
The driver hasn't been digitally signed by a verified publisher. The driver might have been altered to include malicious software that could harm your computer or steal information. In rare cases, legitimate publishers do alter driver packages after they've been digitally signed. You should only install a driver that hasn't been signed if you got it from an original manufacturer's disc.
Unfortunately, there's no trustworthy source of information that indicates who has published an unsigned driver. Anyone can alter the contents of an unsigned driver. The original version of an unsigned driver might have actually come from the manufacturer of your device, but if the driver is unsigned, someone might have altered it. There is no way to know if it was altered for malicious purposes. Most manufacturers now digitally sign the drivers they create before releasing them to the public.
A driver that lacks a valid digital signature, or was altered after it was signed, can't be installed on 64-bit versions of Windows. You will only see this message if you try to install such a driver on a 64-bit version of Windows.
If you see any of these messages when attempting to install a driver, you should visit your device manufacturer's website to get a digitally signed driver for your device.
For more information, see Update a driver for hardware that isn't working properly.