My Software toolkit contains.....

Ad-Aware 6 Personal One of the best malware remover.
AIDA32 System Information utility
AnalogX NetStat Live NSL is a small, easy to use TCP/IP protocol monitor which can be used to see your exact throughput on both incoming and outgoing data
AnalogX PacketMon Logs certain network activity - for Network Admins
AVG Anti-Virus Freeware Anti-Virus software from
Belarc Advisor The Belarc Advisor builds a detailed profile of your installed software and hardware, including Microsoft Hotfixes, and displays the results in your Web browser.
ChessGenius Classic  
Compare It! Excellent utility to compare two files [most types]
Cygnus hex editor Hex Editor
Download Accelerator Pretty good Download manager. (classified as adware by some sites)
Google Toolbar Google search toolbar, also blocks pop-ups in websites
HijackThis This is a great tool, lists all browser Add-ons, search URLs, homepage settings, Browser Helper Objects loaded with Internet Explorer. Using the HijackThis addon-ons log, one can troubleshoot/identify a malware quickly. (Reqd. Skill level - Advanced) See HijackThis Tutorial.
IEFIX General purpose fix for Internet Explorer - Solves New Window opening issues
System Mechanic Trial 3.x Contains a set [10] of powerful features. System maintenance utility
MS Baseline Security Advisor Scan for common system misconfigurations in Windows Platform OS
Nero Burning ROM [with In-CD] Nero CD burning software []
OEBackup Utility [Freeware] Outlook Express Backup utility
Responsive Knowledgebase Simple KB with text search features in Q&A format
Spybot Search & Destroy Excellent utility to remove parasites from the system and has more features [Lock IE Homepage, Internet Options, Immunize bad pages, HOSTS file updates etc]. Update provided via software UI.
Spyware Blaster Prevent spyware from being installed. Set the "Kill-Bit" [Illustration]
TCPView Great utility from Sysinternals, which lists out the TCP communication occurring in a system. Use this to trace which software is doing what, detect malware, trojans and which IP they connect to.
ToolbarCop Internet Explorer Toolbar, BHO remover. Deal with malware toolbar, BHO [Browser Helper Objects] with a feature to selectively exclude/delete particular BHO.
TweakUI for Windows XP SP1 TweakUI for SP1, just what is says. Excellent utility from Microsoft to tweak the User Interface - Cosmetic tweaks and fixes
ZoneAlarm [and ZoneLog Analyser] ZoneAlarm firewall [freeware version]. Add-on ZoneLog analyses the ZoneAlarm log and displays the IP Addresses which attempted to access your computer or port-scanned your PC. Not all IP address listing mean hack attempts. Look for repeated number of the same IP address and do a Lookup of that IP.