I have succeed to prevent Ad-Aware (free version) auto start easily by following steps：

1. Open the Ad-Aware window.

2. Click on the Ad-Watch live icon to turn off it. (Just one click ， not double-click)
Click to view attachment


3. Restart your computer， that's all.


Notice：
Do not to turn off Ad-Watch live by the icon of working tool bar at the bottom of screen，
I don't know why it can't stop Ad-Aware auto start.

Thanks.