I think I may have a Trojan horse or a worm, how can I tell and what do I do?

Hi and thanks for clicking...Lately my computer has been slow as hell and I have run virus scans and stuff...

I have AVG 7.5 [for anti-virus] and Ad-Aware 2007 [for spyware] I have run both numerous times, AVG does not detect anything and Ad-Aware does not detect anything MAJOR, just some cookies that are adding up.... One thing that is bugging me is that whenever I open Internet Explorer, It keeps "Not Reponding" ... those with Windows share this pain with me... [and yes I have de-fragged...but it analyzes the disks, scans and de-frags...but then says "Your computer could be improved, analyzes again and repeats over and over]

Here is my Computer Criteria:

Toshiba Satellite Notebook with Windows Vista Home Premium...On it I have AIM 5.9 and 6.0, Yahoo Messenger, Skype, AVG and Ad-Aware, iTunes, the whole Microsoft Office bundle and some Ativa software for my wireless stuff...

So any ideas? Do I have a worm or a trojan horse? How can I get rid of it if Ad-Aware is not detecting it?

I think I may have a Trojan horse or a worm, how can I tell and what do I do?free anti virus

Windows gets slower and slower over time. The best way to get the speed back is to start over with a fresh install. I had a similar notebook which I installed software on that took 45 mins to install. After defragging and various registry cleaner, it took 40 mins to install. After formatting and reinstalling Windows, it took just 12 mins to install.