From what I've read, you can buy "firecracker" software and utilize your computer to contol your X10 components. I have not tried this personally Because I have an ACIII Pro now.
NYA!, NYA! NYA!...NYA!, NYAAA! NYAAAAA!

(LOL, just kidding)
But keep in mind that all you would have is X10 control for "dumb items"....you wouldn't be able to monitor pH, ORP, Temp, etc. which are needed to properly control reef equipment. A FAR better/cheaper option would be to buy an AC Junior controller for a couple hundred bucks. The features on this unit are the "best-bang-for-your-buck" hands down! I'll be the first to admit that I was in a state of temporary insanity when I paid all that money for the ACIII Pro; it's web capabilities drew me in like bees to honey, damn it! :spin2:
The X10 system was originally designed for home automation and security. Aquarium controllers on the other hand utilize X10 capabilities as a convenience item, not as the main feature. Neptune's Direct Connect is still far more reliable because of electrical noise that sometimes interferes with the X10 signal.
As a matter of fact, Neptune is starting to phaze out the use of X10 because this unfortunate weakness in the system.
BTW: Those links that I posted are just a few of many that sell X10 components...if you want more detailed information about how the system works, you can try
www.X10.com and sift through the endless webpages of information that's available.