avast! for Kerio - System Requirements

For a computer with Windows NT 4: PC 486, 64 MB RAM, 10 MB of free hard disk space, Service Pack 3 and higher installed

For a computer with Windows 2000/XP/2003: PC Pentium, 128 MB RAM, 10 MB of free hard disk space

At least one of the following products:

Kerio Mail Server, version 5.7.3 or higher
Kerio WinRoute Firewall, version 5.1.8 or higher