Sometimes you just want to do something simple in a batch file, and I'd always thought it wasn't possible to 'delete' a value in a .reg file (as the file is applied as a 'merge'), but it is...
Just replace the value with a - (minus)...
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoDriveTypeAutoRun"=-