Computer Stops Responding

This computer has begun to need re-booting many times per day. There are numerous problems commencing with startup, so I'll begin there.I run Ad-aware 6, Spybot S&D and HijackThis frequently in order to try to prevent intrusions, but something seems to have failed!Upon startup, there is (recently) always a ZoneAlarm message saying that "explorer.exe is trying to access the internet" Although I have clicked the box for my (Deny) response to be remembered, the message has appeared at each startup for the last month or so, and I'm tired of that.Likewise, ZoneAlarm asks for permission to allow Firefox to access the internet shows up each time I start that even though I've told ZA to remember it.