1) When you power on, does the 1 green and 2 red status LED blink for 1 second and then the 2 red status LEDs will turn OFF leaving only the green status LED on? If so, it shows that the CPU is functioning properly.
2) On the Toshiba laptop, can you run TRiLOGI 4.13 in a DOS box and attempt host link commands with the PLC. If it works in a DOS box under Windows but does not work when re-started in pure DOS, then check the BIOS setup to make sure that the PC's COM port is enabled while in DOS.
3) For version 5.1 under NT, do you mean you are unable to open the COM port at all? Or do you simply mean you are unable to get a response from the PLC? What is the error message shown in the "Response" window?
4) Please email you contact phone number to support@tri-plc.com and we will call you on the phone to further investigate the cause of your problem.