XP and serial communications breakdown.

I am running embedded XP on a Pentium Windows computer. After moving from Windows 98 to XP all serial comm from the serial port fails. WriteFile sets the correct number of characters written, but no output.  I can remotely debug my program on the pentium machine with my PC, and WriteFile reports the correct number of chracters send, but nothing comes from the serial port. I have tried a NULL modem cable and a straight cable connection while running hyper-terminal on both machines with no luck at all. What are the issues in migrating serial comm from Windows 98 to XP? What do you think I should try to fix my problem? After 2 days I'm out of guesses.
royonlanierAsked:
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vadim_tiCommented:
it is looking like a problem with BIOS setup of your embedded,
i have seen such a problem with DLOG computers

check BIOS setup, may be you think your port (port you connect a cable) is  COM1 and really it is another port.
so you write to one port, and cable is connected to another one
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royonlanierAuthor Commented:
Also, VC++ WriteFile returns a true, non-zero value.
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royonlanierAuthor Commented:
Also, I tried   type com.ini > com1   that returns without error, but no data comes from any of the embedded computer's serial ports to the PC. The same NULL modem cable and the same command works when I replace the embedded computer with a notebook.
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Jaime OlivaresSoftware ArchitectCommented:
Have seen the same problem, serial communications in XP is more strict. But I recommend you to use a ready-made serial library. You can find many at codeproject.com (for Visual C++):
http://www.codeproject.com/system/chaiyasit_t.asp
http://www.codeproject.com/system/serial.asp
http://www.codeproject.com/system/cserialport.asp
http://www.codeproject.com/system/serial_com.asp
http://www.codeproject.com/system/simpleserialcomm.asp
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