In Windows,Open control panel and find "computer managment", then click on on "device manager",scroll down till you see it COM port and USB port.each one you can adjust it. What I think ,you got no right data transfer speed. Have to be 11522 bits per second. After you set it up,dont forget to restart comp.
Or, if don't know nothing about, open "control panel" find and click icon "system properties" look in tabs "general", down you can see it "support Information" if you click it you will get telephone number. Just grab the phone and call. Tell them, you want to connect to remote computer using null-modem cable, send or receive various types of data (ASCII string, binary, octal and hexadecimal) over a serial line. They will go with you over the telephone step by step. Good luck.