ClamAV
ClamAV 1.0.26 for Windows
The Summit Open Source Development Group
ClamAV For Windows is a completely free and open source anti-virus software package
It features a command line interface for scanning files, updating the virus definitions, and a daemon for faster scanning needed on high performance systems. Suited for advanced users only!

Software Summary:

You can run ClamAV on Windows operating systems. ClamAV is a software product developed by The Summit Open Source Development Group and it is listed in the category. ClamAV is a free software product and it is fully functional for an unlimited time although there may be other versions of this software product.

Alternatives in on Windows