Well, you need a laptop running Windows (XP is best I think). I have a Mac OS X MacBook Pro so I downloaded vmware for free (thank you Oregon State DC++) and used an old XP CD from a desktop I used to have.so how does this vag-com work do u download it the hook ur computer to ur car up to like take it out bring it in and tune it or use a labtop lol i am kinda lost and wanna now how this all works before spending money
Next, you need to purchase a cable to connect your car (OBDII port) to your computer (serial or USB port). A company named Ross-Tech sells an OBDII to serial cable. If you do not have a serial port on your computer, there is a converter cable for about $20 that goes from serial to USB. I bought a OBDII to USB cable on eBay that was made by someone other than Ross-Tech (Alpha-Bid). It was $20. The tricky part is downloading the correct driver (there are two drivers for a single USB cable) for the cable.
If you have a USB cable, you must install the driver. Once installed, the USB cable still acts like a serial cable (the software is designed for that) and is given a com port. Drill into the hardware profile and locate the com ports. One will list the USB cable. My cable ended up being on com port three. Remember what com port your cable ends up on.
Once the cable is set up, you must download software. Ross-Tech makes software called Vag-Com. There is a free version that has some features disabled. If you buy the Ross-Tech cable, the driver for that cable is on the site. If you buy a 3rd party cable (non Ross-Tech) you must get the driver from the people you bought the cable from. I highly recommend the alpha-bid USB cable. They give very good directions on how to install the cable and use it in conjunction with the Vag-Com application.
Plug the cable into your laptop and then into your car. Start the Vag-Com program. It will make you test the cable before you can do anything else. This is why you figured out what com port your cable is installed under. Before you click "test" you must select the appropriate com port. Do not select USB, as it will not work unless you have the Ross-Tech cable. Once the test completes successfully, you will be able to use the program.
I have the free version working with a cable I got for less than $20 shipped on eBay. Glad I didn't waste money on the Ross-Tech cable or a serial to USB converter. I should mention that if you buy a 3rd party cable it will work only up to version 409.1 of the Vag-Com software. I may eventually pay $99 for the full version, but not for now. I am happy that I can mess with some things, but there may come a day when I need a throttle body adaptation. Then, I will buy the software. I think it is cool that you can get a free version because it allows you to get everything running before you invest money in the full version of the software.