Periodically cleansing and optimizing the registry of any Windows(c) based PC is a necessary part of system maintenance. The registry acts as a data store, telling the system where to find vital components, what resources to load at boot time, and setting the correct parameters for critical operations. As software and hardware components are installed, updated, and removed, the registry tends to become bogged down with obsolete references, which can slow down and destabilize the system. A good registry cleaning utility can restore the performance and stability of the system by removing these obsolete references and repairing broken links and pointers.
There are several free registry cleaners available, and most of the more popular ones will do a good basic job of cleaning the registry. Users who require the absolute utmost in uptime and efficiency would do well to consider one of the commercial offerings for a couple of important reasons. First, few of the free cleaners provide the full set of features offered in the best paid-for titles. The ability to defragment the registry is one such feature that few of the paid utilities offer, let alone the free ones. On top of that, some of the most popular free ones have have a reputation for mistakenly deleting required entries from the registry. Finally, at least one of the commercial utilities (RegistryBooster from Uniblue) is a Microsoft(c) Gold Certified partner. The registry was invented by Microsoft, and their partners have access to technical information and support unavailable to other entities. This should be a consideration when choosing your optimization tools.
The level of user interaction is another factor to consider. Some of the free cleaners simply run through a scan, optimize what they can, and say that they're done without reporting to the users what actually changed, or giving them the option of selecting which optimizations to make and which to keep. Most of the commercial utilities do give you greater control, letting you pick and choose the changes you want them to make.
With commercial utilities, you usually get access to technical support, should you need it. With freebies, you're stuck trying to get answers to your questions from on-line forums. Forums are great, and a good source of help and information, but that's little consolation when you're trying to revive a failing system. When choosing your registry optimizing utility, you'll want to go with a trusted provider. Find a company that gives a money-back guarantee. Look for products that consistently rate editors' choice awards, as well as user accolades (5 cows on tucows, 5 stars on cnet, etc.)
One final word of advice: You should back up your registry before allowing any registry utility to work on it - even if restoring the registry to a previous state is one of the features of the utility. If the utility does something to corrupt your registry, you might not want to trust that same utility to restore it. Making a backup file of your registry is very easy. From the 'start' menu, click 'run', and type regedit in the entry field. Click the 'ok' button. You will then be running the registry editor. With the navigation pane (left-most pane) scrolled all the way to the top and my computer highlighted, click on the 'file' menu and select 'export'. Enter a file name and click the 'save' button. If you ever need to restore the registry to this state, you only need to double-click on this backup file in Windows Explorer and answer yes to the confirmation prompt. This is simply an extra safeguard, since most registry utilities can do this too.