Non-existant COMM3 appears to be present and looping back Data

I have an application which needs to scan all 16 possible COMM ports on a PC. It is meant to run on different machines, who may be physically configured with 1 to 16 COMM ports.
I have a problem, when I try to access COMM3 on notebooks(OS's used include Win98 and XP Home). Normally, when I try to open a port up using the MSCOMM32 .PORTOpen method, if the port is there, I get a true and perform the required transmission. If it is not there, I will get a code 8002("Invalid Port") and handle the failure. Even though COMM3 doesn't physicallly exist on the notebook(Also, it is not there, when I check the COM ports in the Device Manager dialog box), the .PORTOpen invocation for COMM3 returns true, and further, if i send stuff out COMM3, it loops back to the receiver on COMM3.

1. Can anybody explain why this is happening
2. Is there another method, besides the one that I am using, to determine from the VB program, as to whether a COMM port is available for communication on the PC? The Device Manager COMM port listing knows how to access this information and display this information. Is there a way for me to?

More Information: COMM3 appears to be the dial-up modem. This explains, why information is echoed back. So, the question is reformulated as "What parameters in Windows can you access to distinguish as to whether a COMM port is an ordinary RS-232 port or is a Modem". Again, the Device Manager is able to separate these two items, the first under the Ports(COM & LPT) category and the Latter under the Modems category.

I suppose I could just send an Hayes AT code out and check for the response, but that sequence could bother devices hanging off the standard RS-232 ports.