AVG and MalwareBytes detected a trojan, but other programs didn't. Should I be concerned?

Episode 898 (1:19:50)

Kevin from Huntington Beach, CA
ESET Nod32

AVG free turned up trojan.dropper when Kevin ran it on his system. He also tried scanning with MalwareBytes which confirmed it, so that makes it more of a concern. He downloaded Microsoft Security Essentials and ESET and tried scanning with each of those, and didn't find anything. He only should have one antivirus installed at a time, because sometimes antivirus programs will find files in another antivirus program and flag it as a virus.

The only free antivirus that Leo recommends is Microsoft Security Essentials. Typically when infected with a virus the only way to be absolutely sure that the system is clean is to do a complete reformat and reinstall of Windows. Since ESET didn't find anything though, Leo thinks he's probably ok now, since ESET would even find root kits that a lot of antivirus programs don't detect.

(Disclaimer: ESET is a sponsor).