Sethku,
Can you check if the newly added drive is appearing in the Preboot driver database , to check this Go to NS Console: Settings -> Deployment -> Driver management -> open tab Preboot , from the list check if the driver is present ;
You can also verify if the driver is present at the location : \\<NS Server>\Deployment\Task Handler\bootwiz\Platforms\Winpe2\x86\Drivers\CUSTOM\Drivers , if the driver is successfully added then it should present at this location.
Once you added the driver in to the preboot driver database in to the DS 7.1 you need to reconfigure the preboot environment , Go to settings -> Deployment -> Create Preboot configuration select PEinstall configuration which is the default Preboot configuration (Assuming you are using Windows PE, if you are using LinuxPE then select Linux default preboot configuration) click on 'Recreate Preboot Environment' ; Ans save changes;
Also verify if the driver of correct architecture is added , X86 driver may not be applicable for X64
If you didn't find the driver in the driver database then add the driver form Preboot UI interface from : NS Console: Settings -> Deployment -> Driver management -> open tab Preboot -> Add drivers.
If you find the driver is added properly then , when you boot the client in to Automation , Go to X:\Windows\System32\DriverStore\FileRepository which will have all the drivers source applied in to WinPE.
Also can you provide the link / attache the NVIDIA driver which you are using , so that we will test that in our environment.
Please check and update your findings..