But no matter how good your antivirusprogram is, if you open a suspect email, you make yourself vulnerable to Trojan horses that steal email and bank-access information.
Neither Blackhole or Zeus are new malware (although the authors of Blackhole do use complex tricks to try to get past security software), so any good, up-to-date antivirusprogram such as the free Microsoft Security Essentials tool will be able to detect, prevent installation, and even remove these nasties.