The biggest problem that I had, everytime after I installed my Windows, were the registry files. After a while, the registry kept bugging the operating system until it was full of errors. If I would not have found registry cleaners I would have installed my Windows every time this happened, as working in the registries is risky if you do not know what are you doing.
RegSeeker is always a helping hand in such matters, as it is easy to understand and use, even for beginner users. The registry can be analyzed in a matter of minutes, if not seconds, upon fixing.