Recommendation:
AVG Free Antivirus (Private use) or AVG Antivirus (Business PC)
together with:
Anti-Spam "SpamBully" (Installation in english, german, ...):
Keep Porn Out of Your Family's Inbox. Try SpamBully Free!

• Anti-Virus protects from viruses, worms and trojans.
• Full e-mail protection — AVG checks every e-mail sent or received, providing full protection from e-mail-borne threats. AVG supports all leading e-mail clients, including MS Outlook, The bat!, Eudora, and all other SMTP/POP3-based e-mail clients, such as Outlook Express. Encrypted connections using SSL are also supported.
• Anti-Spyware protects from spyware, adware and other malicious programs.
• Anti-Spam filters spam and protects against phishing attacks.
• Firewall protects from hackers.
• works with Windows Vista™

Features:

• All-in-one, easy to use protection - install and forget
• New program versions and updates, for free, throughout the license duration
• Quality proven by all major antivirus certifications (VB100%, ICSA, West Coast Labs Checkmark)
• 24/7 technical support provided at no extra cost
• Improved virus detection based on better heuristics and NTFS data streams scanning
• Unique automatic threat-removal anti-spyware engine
• Automatic firewall profile switching for improved security and usability

AVG Internet Security AVG Anti-Virus Anti-Virus Yes Yes Anti-Spyware Yes Yes Anti-Rootkit Yes Yes Anti-Spam Yes No E-Mail Scanner Yes Yes Firewall Yes No Compatibility Windows 2000/XP/ Vista Windows 2000/XP/ Vista