This easy-to-use program kills viruses and spyware and stops users from going to webpages that have been infected with hostile software programs known as malware. AVG also prevents you from opening any virus-ridden files or programs already on your PC. Find it at free.avg.com.

Advanced SystemCare by IObit

Aimed at boosting performance as well as improving security, Iobit's Advanced Systemcare can clean up your hard drive and perform other tune-ups. It also scans for spyware and other malicious files. And it protects your privacy by regularly erasing your computer's activity history and Web-surfing traces. Find it at iobit.com.

Avast! Home Edition

This program protects your computer from viruses, spyware, and rootkits, nasty programs that hide on your PC. Avast also prevents malware from sneaking onto your system through instant-messaging programs and other peer-to-peer services. Find it at avast.com.