You can do a quick test to confirm that your PC is really openning the serial port and that your cable is good.

Plug the cable into your PC's serial port and leave other end sitting on your desk. Take a small piece of wire (e.g. a twist-tie) and strip both ends. If you look close, the end of the serial cable, you can see a number next to each hole. Put the two ends of your small wire into holes 2 & 3. Now run Hyperterm and tell it to connect to COM1 (or whichever port you're using). Any baud rate will work, just disable all flow control.

When you type stuff in Hyperterm, you should see it on screen. Pull the wire out and you won't see what you type.

This tells you that your PC's serial port works and isn't busy. It also tells you that your cable works.

It does *NOT* tell you if your serial cable has a null modem twist in it or not.