https://bugs.winehq.org/show_bug.cgi?id=49075
--- Comment #3 from Michael McGuire spoon0042@hotmail.com --- Poking at this more, the drive string (root) gets passed as is to get_mountmgr_drive_type() which assumes the first character is the drive letter, but since it's '' returns 0. GDTW maps this to DRIVE_FIXED (3) if the drive exists or DRIVE_NO_ROOT_DIR (1) if not. (The automatic audio CD assignment is "not" in this case. Done manually it returns 3 though.)
For me anyway, no idea how this is working for the other person on the forum.
A less stupid hack that also works for me anyway but is probably still wrong: add to the top of GTDW
static const WCHAR device_prefix[4] = {'\','\','.','\'};
if (!memcmp(root, device_prefix, sizeof(device_prefix))) root += 4;