There are 3 ways to upgrade the firmware , easiest is Web Interface or PC Pro, sometimes you need to upgrade to perform password reset, to upgrade without logging into the system, this leaves USB method being the only way.
Download the latest Firmware for CP10 or CP20 from the NEC Sharepoint Knowledge web site.
NEC Knowledgebase > UNIVERGE SV9100 > Software > Main CPU > CP 10/CP20 > Rxx_SV9100 > USB Upgrade file
Extract it onto a USB Drive ... all in the root directory
While the SV9100 is still running insert the USB Drive , the first Red LED under the SERIAL interface should solid ON when mounted successfully.
Now it is safe to Turn the system off , wait for all lights to turn off on the CPU , Hold down the load button, Turn on , count to 10 then release the load button.
The CPU will NOT reboot once complete .. ( unlike other methods )
3 LED's will flash in unison once complete ( approx. 3-4 minutes )
Remove USB drive
Turn off system
Turn it back on
DO NOT HOLD LOAD BUTTON WITH NO FIRMWARE USB DRIVE , THIS WILL DEFAULT THE DATABASE