Do Windows 2000 and 2003 block direct acces to serial port?

Hi,

I'm developing a MFC DLL to be the bridge between a Visual Basic 6 application and a industrial machine.

The VB6 app calls some functions in my DLL that makes direct access to the serial port (without using APIs or components).

My friend told me that Windows 2000 and 2003 blocks direct access to serial port. Is this right How can I do to allow my DLL to access serial port

Another question, is there any easier way to test if my VB6 app is synchronized with the equipment that send information throught the serial port

Thanks.