Help Requested with Performance / Strange IE Behavior

Hi folks,

I'm looking for some help with PC performance and some strange behavior on my wife's PC. I just went through a thread over in the Malware section, and it looks like the system is clean at this point, but we're still having strange behavior.

So, here's some background:

The PC is running Win XP Pro. We just went through your suggestions for "basic computer maintenance everyone should do" first, and did some defragging and removed some startup entries that I didn't need. We run AVG for antivirus, ZoneAlarm for firewall, and AdAware occasionally for spyware removal.

Next, I went through your Housecleaning steps. I enabled viewing of hidden files, and then went through your XP malware cleaning procedures.

So, we've been through a bunch of that, and things are still behaving a little odd. Here are some of the things we've been seeing:

-iexplore.exe runs with high CPU %, even when IE isn't being used at all (Firefox is being used instead)
-occasionally Internet Explorer will fail to open, or will take upwards of 10-15 seconds just to launch
-PC is inexplicably slow at times
-at the same time, another WinXP machine on the same network seems to perform fairly well

These symptoms started within the past month or two, but unfortunately, my wife can't recall anything in particular that changed during that time...

Any thoughts?

Your help would be greatly appreciated.

Steve