Which do I download?
 

I've never been very tech savvy. I have a 1999.5 A4 1.8t. I'd like to download one of the free versions and just pickup a legit rosstech cable, i purchased a cheap ebay one years ago and I'm pretty sure it fried something in my original ecu (wouldn't work right, then a professional couldn't connect to the ecu after that).

So how do I know which file to download and which plug to purchase? I'd be using an HP computer FYI