Avira Antivirus shows error on Windows 7

Hello,
I keep getting an error from the setup of Avira antivirus program. I am using Windows 7 and I know Windows OS is vulnerable to viruses. Could I be having a virus already that is preventing this setup from completing? Please assist.

The file could not be copied. … C:DOCUME~1(User Name)LOCALS~1TempRarSFX0ApnIC.dll (or avscan.exe)
