I'm hesitant to post this.
So here are some registry tools and references I have used on specific occasion for my reference.
Kiddos...unless you really know What you want to do in the Windows Registry, Why you want to do it, and How to fix your system if you break it...move on.
Mandatory Disclaimer: MESSING WITH YOUR WINDOWS REGISTRY CAN BE DANGEROUS!
It can even render your system non-operational.
Also, I generally don't find much (if any) performance gains in "optimizing" my registries. I may "defrag" them periodically if it has been a while or if I have installed/uninstalled a bunch of programs, but I really don't see much benefit. So keep that in mind. No magic-bullet performance increase magic here. And some tools and "fixes" might actually break the registry instead of fixing it. So carefully weigh the cost vs. benefit ratio before proceeding on a heavy-duty registry cleanout.
Also, I really tend to use these tools to make my search for particular registry entries or fixes more efficient, but Windows comes with the built-in regedit tool that works very well on it's own.
A Registry Background Reference
From Microsoft KB256986,
The Microsoft Computer Dictionary, Fifth Edition, defines the registry as:
A central hierarchical database used in Microsoft Windows 9x, Windows CE, Windows NT, and Windows 2000 used to store information necessary to configure the system for one or more users, applications and hardware devices.
The Registry contains information that Windows continually references during operation, such as profiles for each user, the applications installed on the computer and the types of documents that each can create, property sheet settings for folders and application icons, what hardware exists on the system, and the ports that are being used.
The Registry replaces most of the text-based .ini files used in Windows 3.x and MS-DOS configuration files, such as the Autoexec.bat and Config.sys. Although the Registry is common to several Windows operating systems, there are some differences among them.
Registry data is stored in binary files.
The Registry Tools
I have used most all of the tools noted here safely and successfully. But that's just me.
Also, due to the structural similarities with the Registry in Windows Vista and previous Windows versions, many of the tools are quite compatible with Vista...but read the developer's page carefully first just to be sure.
And all are freeware/shareware.
CCleaner - A perennial favorite of the Windows optimization crowds. It performs a number of pc housecleaning tasks with browser entries, Windows system files, and the Registry. It is pretty simple to use, but has a lot of options.
Windows Registry Tweaker - A "new to me" tool that allows you to tweak certain Windows Registry settings and assists with restoring previous values back if you don't like the changes. It is pretty intuitive and very clever.
RegSeeker - Tweak and backup your Registry, startup entries, index.dat files, installed applications, etc. Looks for duplicate files and bad shortcuts as well.
ToniArts Easy Cleaner - Great tool that scans your Registry for entries that point nowhere. Often a result of cleaning malware and uninstalling applications. Also lets you remove programs listed from "Add/Remove" program list when they get trapped.
Registrar Registry Manager - Not a Registry cleaner but a Registry manager tool. Allows backup and restoration of Registries, search and replace, bookmarking, color coding support, and a registry defragmenter. Comes in both a $ and "lite" free version. One of my favorites.
RegHance - This LavaSoft (Ad-Aware) tool isn't to be found on their website any longer so I linked to the Major Geeks location. It also has a "nagware" bit to it, however it is a great step up from regedit and is a nice alternative as bookmarking is supported. For more details see this TechRepublic post: How to edit the Windows registry with Lavasoft's RegHance
Specialized Registry Utilities
RegASSASSIN - MalwareBytes' free utility to remove registry keys that refuse to be deleted with normal methods. Often required when dealing with stubborn virus and malware infections. Not an everyday tool, but good to have when you need it.
RegScanner Tool - NirSoft's power registry scanner to help you quickly target and find all instances of a desired Registry string or value entry. Not an editor, but will allow you to open the target in regedit once located.
Windows Registry Recovery - MiTeC tool that reads Windows Registry hives and extracts useful information and configuration values. Supports exportation of hive data and topic data.
Windows Installer CleanUp Utility - Microsoft MSI CleanUp tool. Run this when a program that was installed using Windows Installer fails to come out of the registry. Every now and then I come across an installation issue when running Setup fails as the installer still thinks the application is installed. This helps fix that issue.
ERUNT and NTREGOPT - These Registry tools by Lars Hederer backup and restore the Windows Registry and optimize/defrag it, respectively. Nice, fast and dependable.
Just be careful.