微軟提供了免費的防毒軟體Microsoft Security Essentials正式開放下載，可惜目前沒有繁體中文版。可以下載英文版先試試一下，它提供病毒、間諜軟體和惡意軟體等的防護。
Microsoft Security Essentials provides real-time protection for your home PC that guards against viruses, spyware, and other malicious software.
Microsoft Security Essentials is a free* download from Microsoft that is simple to install, easy to use, and always kept up to date so you can be assured your PC is protected by the latest technology. It’s easy to tell if your PC is secure — when you’re green, you’re good. It’s that simple.
Microsoft Security Essentials runs quietly and efficiently in the background so that you are free to use your Windows-based PC the way you want—without interruptions or long computer wait times.