For $30 (£17), you can pick up a copy of jv16 PowerTools (a more-complete sibling to the streamlined RegSupreme).
In addition to a Registry cleaner and compactor, jv16 PowerTools has other tools that will tell you all you ever wanted to know about the Registry but you probably wouldn't use most of them.
Among the tools are utilities to manage the Registry, find and replace entries, monitor Registry changes, take a snapshot, and get Registry stats.
The collection contains other modules, too, including file finders and cleaners, duplicate finders, and an assortment of system management tools, such as a startup manager and a history cleaner. jv16 PowerTools supports every version of Windows and comes with a full-featured, 30-day trial.
In its aggressive mode, the Registry cleaner in jv16 PowerTools found 392 Registry problems; in its normal mode, it detected 298 problems. The program gave us two ways to fix the problems.
The first option was to back up the Registry and let jv16 PowerTools make all the changes it wanted to - a choice we weren't happy with and wouldn't use. On the other hand, when we chose the 'Custom fix' alternative, the program forced us to look at each problem one at a time. Other apps, such as Registry First Aid, list all the items and let you select specific entries by checking the boxes beside them, which is much easier. We also wished that the program showed the severity of each problem so that we'd know which ones were important, but it didn't.
jv16 PowerTools' Registry Cleaner component includes a slider bar for you to decide how aggressively you want the tool to scan; safe, normal, aggressive, or very aggressive. After the scan, a report shows a graph with the number of errors, from high to low. The feature is interesting but not terribly valuable, since it doesn't offer any details about how it's identifying the problems.
A nice touch, however, is that the opening series of screens provides helpful tips to use the program - read them thoroughly
jv16 PowerTools is a full-featured and useful, if slightly expensive, Windows Registry cleaner.