In this sort of situation, the antivirus that could have prevented it happening is, unfortunately, the user.
Let google be your friend.
I just typed "kazaa problems: there are plenty of adverse reports. (BTW Kazaa is well known to be bundled with spyware.)
The lesson is to search for reviews on any downloaded application before allowing it to download or run. (And then scan it, of course.)
AV's usually aren't great at detecting spyware, a dedicated scanner such as Superantispyware (free and paid resident versions available)
With a lot of work, you might be able to get it operative again. Google is (after Superantispyware) the most likely source for finding info on how to do it. Thousands of users have had this problem.
Good Luck.