AVG Anti-Virus Free Edition

AVG Free Edition is the well-known antivirus protection tool. AVG Free
is available free of charge to home users for the life of the product.
Rapid virus database updates are available for the lifetime of the
product, thereby providing the high level of detection capability that
millions of users around the world trust to protect their computers.
AVG Free is easy to use and will not slow your system down (low system
resource requirements). Highlights include automatic update
functionality, the AVG Resident Shield, which provides real-time
protection as files are opened and programs are run, free virus
database updates for the lifetime of the product; and AVG Virus Vault
for safe handling of infected files. Version 7.5 includes improved
virus detection based on better heuristics and NTFS data stream
scanning, smaller installation and update files, and an improved user
interface. The newest version is also compatible with Windows Vista.