There was a feature at older avast versions it was about scanning when rebooting before the windows starts so it was really helpful to stop any dangerous attempts… do we have the same feature at avast5 free edition?
Hi juventa, welcome to the forum 
Am I correct in thinking you are talking about the boot time scan?
Yes, avast! have kept this in version 5. Currently it is only available in 32 bit systems. (there is a beta out that supports this in 64 bit)
Open avast! → ‘Scan Computer’ tab → ‘Boot time scan’ tab
Scott
Here’s a picture:
(click picture to enlarge)
Like the saying goes, a picture says a thousand words ;D
Especially for someone new when every part of avast! is a new adventure. ;D