The Windows Registry is somewhat like the immigration department of the operating system. This is where all the details of all installed software as well as OS-related process are stored. In fact, every little process that executes in Windows, even the ones you do not see, has to have an entry in this system or it will not be allowed to function.
Since Windows relies on this index so heavily, it is imperative that it stays in good health. Unfortunately, many factors can affect the Registry adversely. Viruses are prime suspects as are other malware. Use a good virus scanner to keep your system and Registry in good working order. A non-threatening way that can disrupt your Registry is the improper removal of software from your system. Manually deleting the folder where the software is located will not get rid of it altogether. Use the uninstall program that came with it or the add/remove option located in the Control Panel.
Another innocuous way where Registry corruption occurs is due to power outages. If the Registry is being updated at the time of power disruption, it can become corrupted. Using a UPS can help avoid this problem. The best way to keep abreast of these issues is to take regular backups of your registry, especially when the system is in good working order. Setting System Restore points before installing any software or any maintenance work is also a good idea. If you do encounter a corrupted Registry, there are a number of free Registry Scanners available on the internet that can fix your problems easily.