Description:
Windows Defender is a free program that helps protect your computer against pop-ups, slow performance, and security threats caused by spyware and other unwanted software. It features Real-Time Protection, a monitoring system that recommends actions against spyware when it's detected, and a new streamlined interface that minimizes interruptions and helps you stay productive.

Description:
avast! is a collection of award winning, high-end technologies that work in perfect synergy, having one common goal: to protect your system and valuable data against computer viruses. It represents a best-in-class solution for any Windows-based workstation.