did below and not working. Then change set DriveLabel=nüvi, not working.
@echo off

set DriveLabel=Garmin nüvi

for %%a in (a b c d e f g h i j k l m n o p q r s t u v w x y z) do (
for /f "tokens=6 delims= " %%i in ('vol %%a: ^|find "drive"') do (
echo %%i | find /i "%DriveLabel%" > nul
if not errorlevel 1 set DriveLetter=%%a
)
)
Then did this
@echo off

set DriveLabel=Garmin nüvi

for %%a in (a b c d e f g h i j k l m n o p q r s t u v w x y z) do (
for /f "tokens=6 delims= " %%i in ('vol %%a: ^|find "drive"') do (
echo %%i | find /i "%DriveLabel%" > nul
if not errorlevel 1 set DriveLetter=%%a
)
)

attrib -S -H .System
attrib -H .System\Diag
not working. then delete "-H" not working.

Maybe i did it wrong.. and Yes my nuvi is in drive "H"