Virus or Norton Systemworks Mess up

This is my first post.

Where do I begin?

I uninstalled Norton Systemworks last week as my licence had expired. I installed AVG and have been using it since then. For a while, I couldn't use Firefox, IE, Outlook, iTunes without the programs running for about 30 seconds then closing unexpectedly. I tried reinstalling them but would get install errors. I also made sure I did a clean uninstall of Norton as I thought that was initially the problem.

I then realized I may have viruses. Since then I've run the following programs in safe mode:

AVG which detected and cleaned 1 virus
AdAware - most recent version with updates
Spybot - most rececent version
Housecall at trend micro
Panda Software - which detected 2 viruses and malware that adaware didn't get

I even deleted my profile and created another.

My programs now appear to have some stability (except iTunes which I can't get to work), but my security center (I'm running XP Pro, SP2), reports unexpected errors and I can't get it functioning again. The SharedAccess registry key is missing and I don't know how to recreate it.

Also, probably because of the new profile, every time I start Outlook and Word, it's as though I'm a new user - it says "preparing to install" everytime I startup these programs.

I'm at a loss. I want to restore my security settings to keep my computer protected. I just want things to go back to the way they were. My computer's never had a virus in over 2 years.

I can post my Hijack this log, if it would help.

Cheryl