Malware detected during the backup process cannot be disinfected.
In Windows Vista, if you are using the Back Up Files option of the Back up your computer feature, the real-time scanning detects all infected files during the backup process and consequently blocks access to them.
As a result, the backup operation fails. This behavior is by design, as real-time scanning needs to prevent access to the infected files. Depending on your settings, the product either tries to automatically handle the infection or asks you what action to take for the infected file. When the product tries to disinfect, delete or quarantine the file, the action fails.
To work around this problem, scan the infected file again by using manual scanning. When prompted, select an action to remove the infection. Finally, run the backup again.