How do you check a file for viruses, worms, trojans, or malware on a computer without preloaded antivirus protection? Simply upload it to VirusTotal, a free antivirus service that analyzes suspicious files using multiple antivirus engines.
VirusTotal is a free, independent service that used multiple antivirus engines. It is powered by real-time automatic updates of virus signatures by their respective developers and gives detailed results from each antivirus engine with real time global statistics.
VirusTotal is developed by Hispasec Sistemas, an independent IT Security laboratory. Remember that this is not substitute antivirus software installed on your computer and will not run background security checks or real time antivirus protection. It is useful service to scan individual files on demand online for free.
I just checked their statistics and it seems Type_Win32 and and Win32/Virut.NAJ are popular viruses detected today and they have detected over 23000 virus infected files in the last 24 hours! You can even email the infected file as an attachment (<10MB) to email@example.com, type SCAN as subject and they will email back the results.
Here are some free antivirus software for your computer.