"Scareware" (or "extortionware" as I call it, fake antivirus/antispy programs like XP Antivirus 2009/2010) prevention tips from redondmag.com, an online IT publication:
- Use a firewall
- Use anti-virus
- Use anti-spyware
- Use a legitimate copy of Windows in order to get updates
- Keep Windows regularly and automatically updated and patched
- When a pop-up appears, check the source and remove it via the system tray; do not click the close button or any part of the pop-up
- Use an alternative browser and lock it down; no Active X, scripts or Java
- Don't give out admin rights
- Consider Windows Vista, or Linux or a Mac