If they can not write to registry, then I assume they also can not add a printer for the comm port. You can use FOPEN(), FWRITE(), FREAD() and FCLOSE().

One problem I had recently regardless of the method I used for sending information to a pole display, was high-bit character always being sent to the display. The settings were correct in the device manager for the port - 9600, N 8, 1. The display would not alway work until I forced these setting using the MODE COMx 96,8,N,1 command in a BATch file. We just had this run every time Windows started up, and this eliminated our problem.

>My application communicates with a device in COM port.
>
>In Windows XP, users don't have registry write privilege to install MSCOMM. So I cannot use MSCOMM ActiveX control.
>
>Is is possible use serial port without ActiveX control ?
>
>Are there any samples how to read/write data to COM port using Windows
>API directly ?