Defender drops a file into your system that you don't have the option of turning off, even when you ctrl+alt+del. For that, I hate it
Try Ad-Aware, it usually finds tons of stuff that spybot can't find, and you can't argue with the price... free
Then again, spybot finds stuff that adaware can't find, so I end up using trendware micro, which costs money but finds everything those two can find and then some. Anyway, Ad-Aware is pretty good.
It definitely sounds like a browser hijack, which any good anti-spyware/ adware/ malware app should find and liquidate.
"In an interstellar burst, I'm back to save the universe"