If things are working well I would not worry about it.
I found the following post concerning nvidia drivers at the link below:
"At a guess, you have your machine set to only accept signed drivers.
To change this, go to the System Properties control panel, Hardware tab,
Driver Signing button. Under Driver Signing, select "warn". This will allow
you to permit the installation of unsigned drivers.
Whether using unsigned drivers is a good idea, I couldn't say. I tend not to
worry about signing (or WHQL certification) as long as I've downloaded
drivers from a recognized source.
Bob Knowlden"
google groups