Install CloudMark's SpamNet..
http://www.cloudmark.com/
This company was started by 1 of the original guys at Napster. These guys use the power of 60,000+ users to identify what is spam and what is not. The more people use it the more accurate it gets.
I used to get over 90 pieces of spam a day, now I only get something like 9-10... and no false positives.
It's free and it's a plugin for Outlook. It's by far the best filtering solution to Spam.
-KC