This mean that display work Ok.

Try this one more time.

Extract rar from Caty post on your empty SD ( you will have only folder Garmin on SD )

Disconect nuvi from Pc and make shure that your nuvi is turned Off

add SD in your nuvi and lock screen with button

now connect nuvi to Pc and nuvi will turn on

if command from SD work your nuvi will turn off and turn on and go to mass storage ( look if you have something writen in update.log)

if update.log is empty, try again with SD inserted in nuvi but this time create procedure for pre boot ( hold screen of nuvi etc )