Virustotal is a web service that provides on-demand scanning of your local files for worms, trojans, and all kinds of malware detected by antivirus engines. It allows you to upload any local file up to 10 megs in size and will perform a scan across 30+ different virus scanning engines (which include all of the leading heavy-hitter virus killer engines on the market).

Rating: 5

AVG is a 100% free antivirus program that offers real time protection, on demand scanning, and email scanning. It also features automatic updates and a very small footprint that will not slow down your system. It does exactly what it promises and does it really well.