Trying to install a driver for old hardware, or otherwise unsupported hardware, on Windows 8? I bet you’ve run across something that kept you from actually install the drivers.
NotSigned

While playing with my Galaxy Nexus, I ran into an issue where I could not install the ADB driver found in the Galaxy Nexus Toolkit. It told me the driver was not digitally signed, and after trying to use it, it said windows encountered a problem.
Failed

This is because Windows 8 enforces driver signing. If it’s not signed, Windows 8 says tough! Well, I found a couple ways to get by this, keep reading to find out how…

Option 1 – My Preferred Option

One easy way is to reboot into the advanced boot options menu and disable the driver signing requirement. It is not persistent and will be gone after you reboot. Since this isn’t something done often, I don’t mind running this every now and then.

Step 1:

reboot into the advanced boot options menu. You can either use the gui or cli, I prefer cli
Reboot

Typical force reboot now command, except with the addition of the -o, which is for boot Options. You can also do this through the PC Settings gui by dragging your mouse to bottom right and go to settings (or hit Win + i), click Change PC Settings, select General on left, then Restart Now on bottom right.

Step 2:

It will walk you through a series of questions or options to figure out what you’re trying to do

Click Troubleshoot
Troubleshoot

Then Advanced Options
AdvanceOptions

Then Startup Settings
Startup Options

Lastly, confirm that you’re wanting to change some stuff
Startup Settings

Step 3:

Now here’s what you’re presented with after the reboot. You’ll want to hit F7 and it will boot into Windows
Advanced Options

Once in Windows, go ahead and install your driver again and you’ll likely see something like this:
Better

So now your driver is installed and you should get this:
Success

Option 2

I don’t like to use this one because it may watermark the bottom right of your screen with Test Mode. You’ll know driver signing is disabled, though, and will persist after reboots. You’ll need to run some bcdedit.exe commands, which BCD is Windows’ Boot Configuration Datastore.

Step 1

Run these commands from an elevated command prompt (Win + x is nice for this):
bcdedit -set loadoptions DDISABLE_INTEGRITY_CHECKS
bcdedit -set TESTSIGNING ON

Reboot and you’re good. Take note there are two (2) D‘s in DDISABLE.

Now install whatever you like. If you ever want to revers what you did, just run the opposite:
bcdedit /deletevalue loadoptions
bcdedit -set TESTSIGNING OFF

I’ve read reports that you only need to turn TESTSIGNING ON and don’t need the DDISABLE_INTEGRITY_CHECKS, but I use option 1, because I don’t like the ‘Test Mode’ on the screen.