What causes registry problems and what does onne do to solve them. See previous question about this.
Thanks.

I'd list causes in order of likelihood to be:

1. The user of the computer manually editing the registry or using registry "cleaning" software without knowing what they are doing (and sometimes even knowing!).
2. Defective software (including malware) or mismatched software components that write incorrect values into the registry for the version of software in use. Incomplete or multiple uninstallations and reinstallation of software of differing versions can lead to a mess.
3. Defective hard drive or file system damage corrupting the registry files.

If the problem can be isolated to a specific registry key(s) and a fix is known for the issue, manually editing the registry to include the correct information can be quick fix. However, wiping the drive and reinstalling the OS is typically the course.