Ah, Nahimic must be running as a different user(makes sense, as it's part of a driver package that'd run for everyone on the machine), so you'll need to run the .bat as admin.
If you want to have it always start as admin, you can make a shortcut to the .bat, right click the shortcut, click "Properties", click "Advanced...", and check "Run as administrator"(the compatibility option "Run this program as an administrator" will be greyed out for batch files).
This does mean you'll get a UAC prompt(unless you have UAC disabled), but it's fewer steps than doing it manually, still.