DEP and Firefox on Startup?

Hello.

Recently I have been having a problem with Elder Scrolls 4: Oblivion.
I could not Alt-Tab out of the game, and if I had FireFox running in the background, I would have no keyboard control (couldn't press Esc to skip the intro screens).
I ran the following programs, to look for virii:
Adaware
Spybot
Zonealarm
A-Squared Free (Deep Scan)
Windows Malicious Software Removal Tool
I found some, which I removed, but still it did it.

I defragged my HD with O&O (took 9 hours!), and still I had the problems.
I tried uninstalling the game and reinstalling fresh, still the problems.


In the end, I tried turning DEP (Data Execution Prevention) back on. I restarted my computer, and when my computer booted up it caught Firefox trying to execute at least 3 times in a row. Then I got several Windows Error Report boxes fore Firefox. In each one, the module that crashed was called '450381a3'
Now Oblivion runs fine. I can alt-tab out happily, and the game doesn't crash/muck up.

Is Firefox supposed to run on startup? Could it be a virus trying to do it?

Please find my HJT log attached, which was run and saved with Firefox blocked on startup. Let me know if you want one without Firefox blocked.