Please try this:
1) Download this program: http://download.spamfighter.com/spamfighter/client/Tools/SPAMfighter_Remover.exe
2) Close your mail client (Outlook / Outlook Express / Windows Mail / Thunderbird).
Run the program just downloaded and wait until the program completes and asks you if you want to sent the logs to the support team (choose: No).
3) Download and install the latest version of SPAMfighter from here: