In expert mode Registry Healer can scan the registry for Empty Keys. Keys that have no meaningful values or data. The registry is full of such keys. Deletion of such keys is not always safe. Some programs and the system may be in need of their keys without values.
Unfortunately, there's no easy way to find out what empty entries are safe to be deleted. You can safely delete empty keys from uninstalled or removed applications - if you know their names, of course. Looking through the list you can find the such registry keys. If the list is very large, just do not delete any. This feature is for advanced cleaning only. You will not get any problem if you have empty entries in the registry.
Empty Keys that are known as dangerous to be deleted are in the exclusion list and will not be modified anyway. So, you always will be able to boot up the system.
We suggest you to make deletion of empty keys by small portions (5-10 keys) and test the system after every deletion. This will help you quickly find and isolate a problem entry (if any) that should not be modified.