What you want to do is possible, but not easy to figure out. I would suggest using the printer port as it has more inputs and outputs than a serial port, it can go either way and inputs can be simultaneous. Depending on what kind of light you plan on using you will need to make/use a relay board as the parallel port can't light more than an LED. Also you will not want to power the inputs as the ports can only handle about 20mA @ 5 Volts. Windows XP doesn't allow direct access, though with older versions you can use Assembly language. with XP you need to READ ALL OF THESE links and it will tell you what pins on the port you could use and how to program them in different languages. if you read ALL of these links it will give you everything you need to know about the parallel port and how to use it to control your project. It works. I use it to control the movement of motors and turn on indicators. http://www.lvr.com/parport.htm
