Look,
This forum ( Feedback and Support ) is for Feedback and support of DriverPacks...
Not only are you not useing DriverPacks you are not useing it in a supported manner...
all that aside... we don't troubleshoot code for noobs...
HOWEVER: Since it (on the surface) seems like such a Blatant and Obvious mistake here you go...
you wrote
SET DRV=%SystemDrive%\Drivers
.\7za.exe x -y -aoa -o"%SystemDrive%\Drivers" ".\Drivers.7z"
)
the Syntax is
7z [source] [destination]
not
7z [destination] [source]
so you should have written
IF EXIST Drivers.7z (
SET DRV=%SystemDrive%\Drivers
.\7z.exe -y -aoa ".\Drivers.7z" -o"%SystemDrive%\Drivers"
)
Let us know if you get it to work 
IDK if we can help since this is a little off topic,
but your welcome to ask...
and i know we would love to hear that you got it to work
jeff
Moved to "Other"
PS that artical is over 4 years old... and much has happened since then...
take a look in our FAQ about SAD (To be renamed SoFI)
I belive SAD created with M2 will be a better solution for you.
SAD still has a few glitches we are ironing out but you can check it out by clicking on the link on our homepage
http://driverpacks.net
it is the second news item on the page