NTSTATUS
NtDeleteValueKey(
      __in HANDLE KeyHandle,
      __in PUNICODE_STRING ValueName
  );

Routine Description:

    One of the value entries of a registry key may be removed with this
    call.  To remove the entire key, call NtDeleteKey.

    The value entry with ValueName matching ValueName is removed from the key.
    If no such entry exists, an error is returned.

Arguments:

    KeyHandle - Specifies the handle of the key containing the value
        entry of interest.  Must have been opened for KEY_SET_VALUE access.

    ValueName - The name of the value to be deleted.  NULL is a legal name.

Return Value:

    NTSTATUS