I have previously used other antivirus software, such as Norton AntiVirus, which I but just bad experiences have made when you uninstall, so the product lies not completely uninstall, leaving behind several entries in the registry, then the generated permanent error messages.
G-Data ISS running on my machine properly (WIN XP; 2GB RAM; AMD Dual Core 3GHZ). Particularly pleasing is the quick and easy customer service, so I had to reinstall the PC, still my registration number and my clients names, but not my password on the spot and turned the existing data to the Internet-Service Center on the homepage of G -Data. Despite a holiday I had an answer e-mail, in my password was informed, so I was able to download new virus updates within only 2 hours.
For such a service I find G-Data has earned 5 stars.