After reinstalling the AntiVir software from CD-ROM, or from an older installation file you had saved, an update error may occur. A message is displayed, saying that update is not possible. The last entry in the update logfile is: "Critical error: Validation of engine and VDF failed."
For the update to run correctly, you have to uninstall the AntiVir software from Control Panel → Add or Remove Software. Then please download the newest version from the Download section and install it using your license.