I don't find a whole lot on my XP systems, mainly because I uncheck the 'Monitor the system for unauthorised modifications' as my firewall and WinPatrol Plus cover that also.
Personally I wouldn't even bother trying to track it down as it isn't an issue of it being malicious, just that it was initially considered suspicious, so should have been further analysed, if it were malicious then there should have been an avast alert to the screen.
I tend to keep my nose out of the logs (not that interesting/exciting) I only consider it worthwhile checking if avast actually alerts, which for me is highly unlikely, normally only happens when I'm checking something out for the forums.