Hard-core techies who want to know in intimate detail all the changes made to their Registry by newly installed programs will want to get a copy of RegSnap Standard. It takes snapshots of your Registry or your entire system, compares them, and shows you what changes have been made. It can even help you undo the Registry changes, so that you can restore your system to its previous state.
Be aware this is not an easy program to use--its interface and overall use is less than intuitive. So you'll most likely have to struggle a while before you can figure out basic tasks, such as how to roll back the Registry, or create reports of Registry changes. To roll back the Registry, you'll have to tell the program to create a .reg file, and then use that with the Windows Registry Editor
Only those with considerable technical skills should use this program, because the .reg files it creates can potentially cause damage to your system. For most people, a better bet than RegSnap is using built-in System Restore provided in Windows. But if you're of a technical bent, and don't mind getting your hands virtually dirty in the Registry, you might want to give RegSnap Standard a try.