CCleaner, a free downloadable Windows program from CCleaner.com
, has a great registry cleaner with an automatic back-up feature. I have used it for years and it has never caused a problem, unlike other "registry cleaner" programs. The title of the program comes from "crap cleaner," which it does very well.
You access the registry cleaner feature by clicking on the "registry" icon on the left side of the screen, click "scan" to identify problems, and then can "fix" problems one-by-one after reading a brief explanation of the likely source of the problem. You can select the type of item for a scan.
This feature may be a bit unsophisticated for many and not quite what is sought in this thread. In my experience, it identifies left-over elements from removed programs and similar items which can slow down loading. The program has some other features, including a fast way to modify a start menu.
The website is very informative. This well-established freeware program has had over 300 million downloads.