According to this link from support:https://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=1139
Here is supported operating systems and requirements:
"Following system requirements are recommended in order to install and run avast! Free Antivirus 7.x on your computer: Microsoft Windows XP Service Pack 2 or higher (any Edition, 32-bit or 64-bit), Microsoft Windows Vista (any Edition excl. Starter Edition, 32-bit or 64-bit) or Microsoft Windows 7 (any Edition, 32-bit or 64-bit).
Windows fully compatible PC with Intel Pentium III processor or above (depends on the requirements of used operating system version and other 3rd party software installed).
256 MB RAM or above (depends on the requirements of used operating system version and other 3rd party software installed).
210 MB free space on the hard disk, 300MB if also included Google Chrome will be installed (to download and install).
Internet connection (to download and register the product, for automatic updates of program engine and antivirus database).
Optimally standard screen resolution not less than 1024 x 768 pixels."
I hope this is some help to you slybo.
All my best!