Among the installation tasks, Windows creates a system registry. The use of Windows registry is to store information that serves as a reference to different hardware and software for proper functioning. For example, your system registry contains full details of all the hardware installed. If you are setting up an Internet connection, the software will look up the Windows registry to find details about the network cards and modems on the computer. Accordingly, it configures your connection. Similarly, when you click on the desktop icon for MS Word, it goes through the registry to find the default locations of different relevant (DLL) files so that it functions properly.
For ease of use, the Windows registry is divided into five parts. To look at them, click Start, and then Run. In the Run dialog box, type Regedit and hit Enter. You can see the registry with two panes. The left pane contains keys or pointers that are looked upon by the different applications on your computer. The right pane contains data pertaining to a certain key. You can notice that even though there are only five main keys to the left, when you expand them – they seem endless with sub-keys and more keys within the sub-keys. Even for a perfect Windows XP registry, it is normal to have a huge size.
As you install more and more programs on your computer, the Windows XP registry grows much more in size. This causes delay in loading applications as the application has to parse through the many keys/pointers in the left pane to find data it needs. For each un-installation too, the registry is scanned to get the required data. Very often, most of the keys, and thereby data, is left back even after you uninstall a program. If an installation fails, and you run it again without using Windows Installer Cleaner Utility, chances are that you are creating duplicate keys. These duplicate keys and broken links may lead to problems operating individual applications and may even lead to Windows Crash.
These problems compel people to look for proper registry tools that can fix Windows XP registry and optimize XP registry so that the system keeps on running smoothly.
NOTE: Windows Installer Cleaner Utility claims to clean up files and registry entries for any failed installations, especially Windows Applications. To the date of the article, I do not have any solid evidence proving that it really works.