I'd rather risk the virus and be able to actually use the computer for something, lol.
Check out the cable and software at
http://obd-2.com/#products
The website is hard to navigate, but basically, for around $200 you can get a cable and software that will work with virtually any OBD-2 vehicle made. He constantly updates the software and the updates are
free once you make the initial purchase. I've had it since 2003 and I love it. It's way much more than a code reader, you can get volumes of data, you can data log, obtain voltage outputs from sensors, read timing, etc, etc. It does require you to learn a lot on your own though, as support /help isn't that great. It's not quite a Tech II, but it's not $4000 either.
It will run quite well on an older laptop, I was using an IBM 560, Pentium 1, that I bought in 2003 for $50, until I dropped it on a driveway. Now I'm using an IBM 600E, Pentium 2, that I paid $50 for.
No MAC version though, sorry MAC guys.