Thumb drive tools-worth checking out!
Are you the one that your friends and family call every time they have a problem with their computer? Put these tools on your USB thumb drive and troubleshooting will be that much easier.
Please feel free - encouraged even - to suggest other helpful, portable troubleshooting apps.
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AutoRuns (startup monitor)
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Avira UnErase (file recovery)
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CCleaner (PC optimization)
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ClamWin (anti-virus)
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DBAN (secure disk eraser)
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JkDefrag (disk defrag)
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K-MAC (MAC address changer)
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On-Screen Keyboard (virtual keyboard)
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Portable MV RegClean (registery cleaner)
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Portable UnInstall Cleaner (software uninstaller/cleaner)
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Process Explorer (advanced task manager)
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Restoration (file recovery)
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Roadkil's Boot Builder (create custom boot sectors)
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SpyBot Search and Destroy (spyware removal)
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System Spec (System Information Utility)
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TinyResMeter (real-time system and resources)
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What Is Transferring (TCP packet sniffer)

The most comprehensive tool for info on auto-starting locations of any startup monitor/utility. It shows you what programs are configured to run during system bootup or login, and displays the entries in the order Windows processes them. To download and/or get more details, click here.

File Recovery tool for Windows 2000 and XP. Install on a PC, then copy the installation folder to your USB thumb drive. Though it's no longer officially supported, it's still available for download, and it still works. Download here.

The popular PC optimization and privacy tool has a Portable Edition that you can download and install on your USB thumb drive. Related tutorial: How to use CCleaner to free up disk space on your Windows PC

Following the instructions found here, you can carry the open-source anti-virus software ClamWin on your USB pen drive. Great for removing viruses when you're unable to install anti-virus software on the host PC.
DBAN is a self-contained boot disk that securely wipes the hard disks of most computers. Download the USB flash drive version from http://dban.sourceforge.net. Related tutorial: How to completely wipe all the data from your hard drive

JkDefrag is a portable disk defragmenter and optimizer for Windows 2000/2003/XP/Vista/2008/X64. Completely automatic and very easy to use, fast, low overhead, with several optimization strategies, and can handle floppies, USB disks, memory sticks, and anything else that looks like a disk to Windows. And it's open source.
Useful for network troubleshooting. Download here.

Working on a PC with a broken keyboard? Or one that has keys remapped to the strangest of places? On-Screen Keyboard will come in handy. Note: part of the PortableApps suite.
Registry cleaner for 32 and 64bit Windows. Also allows you to make backups of any registry change made by MV RegClean. Download here.

When a program does not properly uninstall or problems occur in the uninstallation, there will be excess entries in the registry. UnInstall Cleaner can delete these entries so that you don't take the painstaking job of cleaning the the registry manually. Download here.
Hugely improved version of Windows Task Manager. Download here. Related tutorial: How to get detailed information on each running process in Windows
Restoration is another file recovery tool, but this one works on Windows 98/ME/2000/XP/Vista. If you're trying to recover files in 2K or XP, try Avira UnErase (see above) first.
Boot Builder allows you to create your own custom boot sector from scratch. This utility allows you to recreate or restore boot sectors lost due to virus or other damage to a drive. Boot sectors can be imported/exported to a disk or created from a template. This program supports FAT and NTFS boot sector types.

Download SpyBot Search and Destroy, install it on your PC and then follow the instructions found here to make it portable. Related tutorial: How to remove spyware from your PC
Find detailed information on the PC you're troubleshooting. Works in Windows 2000 and XP completely, some info won't be displayed (though it does work) on Windows 98 and ME. Download here.

TinyResMeter provides real-time PC system and resource info in a small display window, and detailed info when that window is selected. Download here
What Is Transferring is a portable packet sniffer for Windows 2000/XP. It can capture and display the TCP/IP packets that pass through a network adapte. Very helpful for determining unwanted connections and then viewing what those connections have sent/recieved