The registry on your computer stores information about all kinds of things on your computer - from the fonts you've got installed, to the programs that should run on startup. Most of the errors that registry software repair are related to the same sort of thing. The registry has incorrect information about what's on your computer and where it is.

	Add Remove Programs	The idea with Windows is that when you uninstall a program, it will be removed fully from your computer. It's not always that simple! Sometimes you'll uninstall a bit of software, only to find that it's still listed in your Control Panel's Add / Remove Programs section. And you can't get rid of it. This can be confusing and annoying. This part of the registry cleaner wipes away this final remnance of your software for good.
	Application Path	References on your computer to programs that don't exist any more. Maybe you removed them. Or maybe they are now living in a different folder and nobody told the registry.
	Auto Run Programs	Registry keys with auto-start programs. Invalid entries are selected for correction by default. All other entries are listed for your information only.
	Com & ActiveX	The COM/ActiveX section of the Windows registry can contain invalid entries that can cause application failure, system crashes, or errors when opening documents.
	Dll Problems	Invalid DLL aliases remaining after moved/deleted .dll files.
	Empty Registry Keys	Registry cleaning software finds and removes obsolete entries in it's database. This leaves holes. A good registry cleaner should find and remove any empty registry entries to free up space and resources.
	File & Path References	Some registry items can be associated with non-existing files and folders such as when temporary files are used for storage. These entries may still be valid and required for use. Only remove entries that you know are invalid.
	File Associations	The registry keeps track of every file type, and the program used to open it. The user can edit / change this, or software can also change things when it's being installed or uninstalled. This part of your registry software will check and repair errors it finds in this area.
	Font Files	The registry keeps track of all the fonts on your computer. And if you've removed a font it could be that the registry still thinks it's there. The registry software compares all the fonts on your hard drive to all the fonts in the registry and makes repairs where necessary.
	Help Files	Help files are also registered in your PCs registry. And if there's any references to ones that aren't there any more, they'll be repaired, making things run more smoothly.
	Invalid Shortcuts	Some registry repair software scan for any shortcuts that you or other software have created that aren't going anywhere. It will get rid of these problems, freeing up more system resources & making Windows run more smoothly.
	Shared Folders	References in the registry that refer to shared folders that are no longer there, or have been moved. Registry cleaners can quickly find and repair these errors.
	Sound Section	Windows also stores information in the registry about what sounds to play in windows. This function fixes problems to do with missing sound files.
	Startup Programs	Speedy startups are essential with Windows. The programs that start up when Windows loads can have a huge impact on it's boot speed. The list of these startup programs are all stored in the registry. And all good registry cleaners should have a way to repair and edit this list of programs.
	Virtual Devices / .vxd	This section contains the list of information associated with virtual drivers that are registered on the system. Registry software repairs the registry entries which reference virtual drivers that do not or no longer exist on the hard drive.