Проверка на существование файла

CreateFile(<имя файла>,0,0,0,Open_Existing,0,0)

//
    // Attempt to open the file object by name.  This will yield the handle
    // that the user is to use as his handle to the file in all subsequent
    // calls, if it works.
    //
    // This call performs a whole lot of the work for actually getting every-
    // thing set up for the I/O system.  The object manager will take the name
    // of the file and will translate it until it reaches a device object (or
    // it fails).  If the former, then it will invoke the parse routine set up
    // by the I/O system for device objects.  This routine will actually end
    // up creating the file object, allocating an IRP, filling it in, and then
    // invoking the driver's dispatch routine with the packet.
    //

    status = ObOpenObjectByName( ObjectAttributes,
                                 (POBJECT_TYPE) NULL,
                                 requestorMode,
                                 NULL,
                                 DesiredAccess,
                                 &openPacket,
                                 &handle );

//
    // Open the object by its name.  Because of the special QueryOnly flag set
    // in the open packet, the parse routine will open the file, and then
    // realize that it is only performing a query.  It will therefore perform
    // the query, and immediately close the file.
    //

    status = ObOpenObjectByName( ObjectAttributes,
                                 (POBJECT_TYPE) NULL,
                                 requestorMode,
                                 NULL,
                                 FILE_READ_ATTRIBUTES,
                                 &openPacket,
                                 &handle );