Just a kind of listing, nothing more. I'll go first.
Antivirus: Bit Defender
Firewall: Default WinXP + Bit Defender
Registry & Disk Maintenance: TuneUp Utilities 2006
Email: Gmail
Instant Messaging: GAIM
Office/Productivity: MS Office 2003
BitTorrent: Azureus
Browser: Avant Browser
Spyware Remover: Ad-Aware, Spybot Search & Destroy
Media Players: Media Player Classic, VLC, Winamp
Edit: added some additional utilities...