Thread: Error message: 'Your computer might be at risk'

Windows doesn't include any anti-virus software, and if no anti-virus program is installed, a warning bubble will appear near a red shield icon in the Taskbar to alert you. Vista's message is slightly different, and says 'Check your computer security' instead. In either case, having virus protection is absolutely imperative. Thankfully, free programs such as AVG Anti-virus are available to download.