If you have updated from Windows 8 to Windows 8.1 Preview, antivirus software is not working on the new OS. I have tried many apps, such as Avast Anti-Virus, AVG, BitDefender, Norton 360, and Micro Titanium Maximum Security Suite, and nothing launchs, even setup with the compatibility settings.
Windows Defender and Firewall are the built-in anti-malware product with real-time protection on Windows 8.1. If you would like to use other anti-malware software with a full protection on Windows 8.1 Preview, try the following apps which are fully compatible with Windows 8.1 public preview.
* Symantec has released the beta versions: Norton 360, Norton Internet Security and Norton AntiVirus. These products are available for and use less memory consumption. * offers all-in-one solution. It not only provides antivirus protection to secure your computer, but also has personal Firewall and Anti-Phishing features. * This version is only for testers and has new features, like File Shredder. You need to sign in to download it.
The also works fine on the Preview at Build.