With Avast Home Version running on XP-SP3, there are two locations where logs/reports are stored
they are:
C:\Documents and Settings\All Users\Application Data\Awil Software\Avast5\Report\
and
C:\Documents and Settings\All Users\Application Data\Awil Software\Avast5\Log\
I don't know if they are in the same place in the Pro Version, but since no one else had offered you any suggestions, I hope this helps.