RockXP by Korben
Rock XP is a handy little tool that I use for two things. First, it shows the license key for the Windows that is installed, and second it can search your system and reveal passwords that a customer has forgotten. This has happened many times, usually with MSN and Rock-XP has made things much easier.
Note: (from the author’s website) “Small Warning: RockXP is a tool that allows you to retrieve password. To do that, RockXP uses a third part tool called Pwdump2.exe which is an opensource software (Sources are included in RockXp). This tool retrieves HASH password of Windows. Unfortunatly, some Antivirus detects this tool like a Virus, but it’s not. So if you have downloaded this software from this website, i guarantee a 100% free of virus software… So, now you are free to use this tool… Thanks to you.”

Ccleaner by Piriform LTD
Ccleaner, also known as Crap Cleaner, is great program for freeing up extra space on a hard drive. It scans your temp folders and cookies then tells you how much free space you gain by deleting them. I like to run it before doing a hard drive scan for two reasons: One, it makes the scan faster by having less files to analyze, and two, often times malware and trojans like to hide in the temp folders of Windows.

Winrar Trialware by RARLab
I used to use Winzip for for my archive compression needs in Windows, but WinRAR handles more file types. Not to mention, Winzip does the irritating “feature” of putting unnecessary junk in the taskbar! What is with all the different file compression formats anyway? WinRAR supports: RAR, ZIP, CAB, ARJ, LZH, TAR, GZ, TAR.GZ, BZ2, TAR.BZ2, ACE, UUE, JAR, ISO, 7Z, and Z.

Winsock XP fix freeware by Option Explicit
A common software problem with Windows computers is corrupted internet settings. We used to have to fix these by hand in a 15 step process, but we now can use this utilty to save time repairing messed up winsock settings in the registry. Everything is checking out but you still can’t get online? Run this program.

SiSoftware Sandra Lite shareware by SiSoft
I’ve been using Sandra since way back when, the utility has a lot of nice functions built into its easy to use interface. This program gives you a wealth of information about your computer and has some nifty utilities to benchmark your individual hardware components, such as CPU, RAM, etc. I use this program often to benchmark a system if the customer complains it is running slow to narrow down where the performance bottleneck is coming from.

PassMark BurnIn Test Shareware by Passmark
We often get systems that only lock up intermittently, which can make it hard to track down the problem. Running BurnIn test puts a load on the various components in the computer and helps in the process of elemination. You can also specify which components to test and adjust the amount of load they place on the system. I like computers that just flat out break, not this “work fine for hours and offer no clues” garbage.

AVG AntiVirus freeware by Grisoft.
Grisoft has a free for private individuals version of their anti-virus software, complete with automatic virus signature updates and realtime scanning protection. It has a low memory footprint so it won’t slow down your system while it’s running in the background. AVG Free has an easy to use interface so I often recommend it for computer novices. It doesn’t catch every virus, but honestly no single virus protection software package is foolproof these days.

Tip: It is possible to upgrade AVG 7.5 even if it is giving you a message to purchase their professional version. Just download AVG8 and install over the top of it.

HijackThis freeware by Trend Micro
This is a very powerful cleaning utility that creates a list of items loading in your system and gives you a means to remove them. A fair amount of knowledge and willingness to research the entries is required to use this tool effectively. Originally created by Merijn.org

Warning: It’s possible to remove the wrong thing and damage your system, so I only recommend this utility for experienced users. Hijack This has a logging ability that is often used on message boards and support forums to let the community help analyze an infected computer.

BootIt NG trialware by Terabyte Unlimited
As you may be able to tell from it’s name, this is a boot menu system for running multiple operating systems on your PC. However, that isn’t Boot-Its most useful function. It also includes powerful disk managment software that I use to copy, resize, and convert partitions. Very handy when you’re upgrading to a new hard drive.

Beyond Compare trialware by Scooter Software
What a great little piece of software, I’m amazed something like this didn’t come along sooner. Copying the complete contents of drives in Windows sucks. You’ll get about half way through a 40gb copy, and the windows copy feature will error out on a file. Of course Windows doesn’t copy the files in order, so you have no idea what’s missing. Beyond Compare solves that problem. Very, very handy.