Supported operating systems for avast! Free Antivirus 5.0 and avast! Pro Antivirus 5.0 are Microsoft Windows 2000 Professional Service Pack 4, Microsoft Windows XP Service Pack 2 or higher (any Edition, 32-bit or 64-bit), Microsoft Windows Vista (any Edition, 32-bit or 64-bit) or Microsoft Windows 7 (any Edition, 32-bit or 64-bit).
Supported operating systems for avast! Internet Security 5.0 are Microsoft Windows XP Service Pack 2 or higher (any Edition, 32-bit or 64-bit), Microsoft Windows Vista (any Edition, 32-bit or 64-bit) or Microsoft Windows 7 (any Edition, 32-bit or 64-bit).
Note:
It means, that avast! 5.0 isn't supported (isn't compatible, couldn't be installed and won't run) on DOS, Microsoft Windows 3.x, Microsoft Windows NT 3.x, Microsoft Windows NT 4.0, Microsoft Windows 95, Microsoft Windows 98, Microsoft Windows ME, Microsoft Windows Server operating systems or others which aren't specified as supported.
Is it required to uninstall avast! 4.x before installing avast! 5.0?
Yes, but there isn't necessary any user interaction to uninstall avast! 4.x, because installer of avast! 5.0 is able to detect previous instance of avast! 4.x and uninstall it automatically.
How do I register avast! Free Antivirus 5.0?
Open the avast! Free Antivirus 5.0 interface and click on the 'MAINTENANCE' tab. Next click on 'Registration' and then on 'Register now'. A new window with registration form will open. Into the form fields fill the required data and then click on 'Register for free license'.
avast! Free Antivirus 5.0 can now continue to be used for 12 months and you will continue to receive automatic updates to both the program and your virus definitions. At the end of that time, it will be necessary simply to register for a new free license.