Well. I'll teach both ways, because people have Windows XP, and Vista. >:].
For Windows XP:
Go to Start - Run - Type in cmd, press enter.
Type in telnet.
Press enter.
Type in o.
Press enter.
Type in towel.blinkenlights.nl
Press enter.
Now, Star Wars will begin to play.

.
But for Vista users, it's a bit more complicated. You have to enable telnet for this to work. >:[.
For Windows Vista: Go to Start - Control Panel - Programs - "Turn Windows Features On or Off". Wait for it to load. Then, scroll down to the bottom, and put a checkmark beside "Telnet Client". It'll take awhile to change your settings..So be patient.
Now, go to start - run - cmd. (Use the search feature to find them.)
Type in the following into cmd.
Type in telnet.
Press enter.
Type in o.
Press enter.
Type in towel.blinkenlights.nl
Press enter.
It'll now start playing the movie.

. (It starts after about 20~ seconds).
You now have the tutorial so it works on both Windows XP & Vista. Enjoy.