On-access scanning protects your computer from viruses by detecting and treating viruses that may be dormant on your computer. On-access scanning is enabled by default.
To enable on-access scanning:
Select Antivirus|Main.
In the Protection area, click Antivirus Options.
The Advanced Antivirus Settings dialog appears.
Under Advanced Settings, select On-Access Scan.
Select the Enable On-Access Scanning check box, then click OK.