[Unattended.bat file CD Drive letter discovery how to]

Perhaps try this in your bat

@Echo Off
CLS
Mode 62, 9
Color F9

Set Char=C: D: E: F: G: H: I: J: K: L: M: N: O: P: Q: R: S: T: U: V: W: X: Y: Z:

for %%i in (%Char%) do if exist %%i\SETUP.exe Goto Confirm

for %%i in (%Char%) do if not exist %%i\SETUP.exe Goto Missing

:Confirm
set CDROM=%%i
set AnswerFile=.\unattend.txt
set SetupFiles=%CDROM%:\amd64

%CDROM%:\amd64\winnt32 /s:%SetupFiles% /unattend:%AnswerFile% /copysource:lang

Goto TheEnd

:Missing
set CDROM=Error Unknown Occur
CLS
Echo.
echo %CDROM%
pause
Goto TheEnd

:TheEnd
Exit

Thanks a lot !!