File Management
CCleaner - Cleans up Windows systems. Clears temporary internet files, cookies, history etc..
JkDefragGUI - An advanced defragging tool far superior to the built in Windows one
DriveimageXML - Hard drive imaging tool. Allows you to get a single file out of a whole image too
Explore2fs - Allows you to explore hard drives with Linux file systems
Double Killer - Finds duplicate files and deletes them
Deep Burner - CD/DVD Burning software
7-Zip Portable - Archive creating and extraction tool. Can handle most compression formats
PC-Decrapifier - Cleans out the crap that comes installed on new brand name computers (Norton trials, toolbars etc.)
Information
Process Explorer - Allows you to view system processes
System Information - View lots of information about a system (specs, passwords, temperatures etc.)
ProduKey - View software cdkeys and serials
Autoruns - Autostart program viewer
HWMonitor - View hardware information
GPU-Z - Show video card information (chipset, bios version, shaders, memory size etc.)
Wireless Key View - Shows saved wireless network keys
TreeSize Free - Show how much space each folder on a system uses
Game Key Revealer - View CDKeys and Serials for popular games
USBDView - Allows you to list and manage USB devices (including devices that arent currently plugged in)
TrID - Identifies file types for extension-less files
Codec Installer - Finds and analyzes video codecs
Unknown Devices - Tells you what a “Unknown Device” in system properties actually is
GSpot - Video analyizer
Repair Tools
Norton Removal Tool - Removes Symantec products
McAfee Removal Tool - Removes McAfee products
LSPFix - Fixes broken Winsock entries
Dial-a-Fix - Repair Windows files and registries
Recovery
Recuva - Recovers deleted files
Restoration - Recovers deleted files
Photorec - Recover deleted/damaged files from Flash memory (like digital cameras)
DBXTract - Recover emails from damaged DBX files (like Outlook Express)
Network Tools
Wireshark - View network packets
Network Scanner - Scans the network for devices
Putty - SSH/Telnet/RLogin client
Network Stumbler - Wireless Network Scanner
Virus and Malware Removal Tools
Clamwin Antivirus - Virus scanner/remover
Rootkit Revealer - Detects rootkits on a system
Combofix - Malware finder and remover
SmitFraudFix - Malware finder and remover
RogueFix - Malware finder and remover
Hijack This! - Malware remover
SUPERAntiSpyware - Malware scanner and remover
Malwarebytes - Malware scanner and remover
Misc
Mozilla Firefox - Web browser
JavaRa - Find and remove old Java versions
Monitor Tester - Test monitors from problems
Dead Pixel Tester - Finds and fixes dead pixels on LCDs
ChkFlsh - Check flash drives for errors or test their real size (as fake ones appear on eBay)
Double Driver - Driver backup tool
SumatraPDF - Lightweight PDF viewer
Revo Uninstaller - Advanced application uninstaller
Prime95
Real Temp
HW Monitor
Tweaks
TweakUI - Windows XP tweaking tool
Vista Tweaker - Vista tweaking tool
Scripts
Quickly Make a System Restore Point - Makes restore point
Reset Network - Releases/Renews IP and flushes DNS
Clear Printer Spooler - Clears stuck print jobs from spooler
Stop Automatic Updates - Stops “Windows has installed updates, restart now” dialog temporarily Start Automatic Updates - Switches it back on
And also Hirens USB boot.