The recommendation is test-sign your driver...
Installing an Unsigned Driver during Development and Test
By default, 64-bit versions of Windows Vista and later versions of Windows will load a kernel-mode driver only if the kernel can verify the driver signature. However, this default behavior can be disabled to facilitate early driver development and non-automated testing. Developers can use one of the following mechanisms to temporarily disable load-time enforcement of a valid driver signature. However, to fully automate testing of a driver that is installed by Plug and Play (PnP), the catalog file of the driver must be signed. Signing the driver is required because Windows Vista and later versions of Windows display a driver signing dialog box for unsigned drivers that require a system administrator to authorize the installation of the driver. This PnP driver installation behavior cannot be disabled on Windows Vista and later versions of Windows.
How to work-around to install and load unsigned driver on Vista64?
1. To install unsigned dirver.
gpedit.msc -> User Configuration -> Administrative Templates -> System -> Driver Installation
->Code signing for device drivers.
2. To disable load-time signature enforcement for a kernel mode driver.
- Use F8 Advanced Boot Option. This setting does not persist across system restarts
- Attach a Kernel Debugger to Disable Signature Verification