I got rid of G Data Antivirus for several reasons, one being that it was consuming system ressources like people consume air. When an update is running, which happens about every 10 minutes, you can go and prepare dinner, take the dog for a walk or visit another country. Take your time, your system will be unusable as long as that "program" is "protecting" your system.
Another fascinating fact about G Data Antivirus is, that it lacks some rather important configuration options. It seems to be impossible to disable the annoying tooltip which clogs up the lower right corner of your screen every time G Data Antivirus analyses something that is bigger than 100 KB. Don't you love little boxes popping up on your screen every time you open a video in your webbrowser? Well, I don't.
G Data Antivirus was apparently also the reason why games like Mass Effect 2 kept freezing up every 10 seconds and the main reason for permanent harddisk activity. Not even O&O Defrag caused that much load on the harddisk and that thing is supposed to cause some load as it is designed to physically reorganize the files on the harddisk in the background.
Since G Data Antivirus uses two scanning engines, avast! and BitDefender, I switched to avast! Free Antivirus and my problems are basically gone.