The internet is full of crap. When I reformat my hard drive, I unplug the network card so my computer is completely not open to the many internet threats out there. Before reformatting, I put the setup files for AVG anti virus, and Zone Alarm on a flash card. After finishing fresh installing windows, I will keep my network card unplugged and install Zone Alarm and AVG (It helps to have the latest setup files so you won't have to update later). After the two programs are installed, I shut down my computer and plug in my network cable and turn my machine back on. That is when I start installing the windows updates. If you have Zone Alarm running I can't imagine a virus being able to get onto your computer.
And are you sure that all of the updates are installed? For some reason, whenever I update, I have to visit the windows update page like ... I think 3 times, restarting my computer inbetween each visit. Each round, they have a different batch, and the third includes SP2 (I noticed you didn't mention having this installed. Maybe you should try going to the windows update page and see if they have that file waiting to be installed on your computer.)
Best of luck. Technology can be a poop sometimes
