1) Avast free antiviruse - Protect your pc from viruse attacks. avast! Home Edition is free of charge for HOME users for NON-COMMERCIAL use. You can find more information here. If you are not a home user, or you use your computer for profit, the avast! Home Edition is not licensed for such use, and you are asked to use the commercial version - avast! Professional Edition. You can get a free serial from avast website. Click here for download avast free software.
3) Free Online Viruse Scanner: Trend Micro HouseCall is an application for checking whether your computer has been infected by viruses, spyware, or other malware. HouseCall performs additional security checks to identify and fix vulnerabilities to prevent reinfection. click here for start a new online scan
4) Trend's Free CD with their all anti viruse products: Trend's Free CD contains evaluation versions of all of Trend's virus protection products, from the desktop PCs to LAN servers to groupware and mail systems to the Internet gateway.Trend's Free CD is available for corporate users only. Click here to get one
***it is adviced that you should only run one anti-virus product at a time. If you are going to do the online scan, disable your ordinary AV product first.