Create and compare registry snapshots, even export changes, with RegistryChangesView
RegistryChangesView is a free utility you can use to keep snapshots of your registry, compare them, export changes, restore them.
Since a lot of programs tend to leave some of their registry entries when you uninstall them, a concept like that offered by RegistryChangesView can prove useful. Just take a snapshot of your registry before you install an application and if you decide to uninstall, then after its uninstaller finishes, restore also your registry backup, or take a new snapshot and compare to find difference and locate remnant of the uninstalled program.
Note that the program lets you even open the registry at the location you are browsing when you compare, to examine live and modify, delete, etc.
Even if you don’t need to compare registry snapshots, you can use RegistryChangesView just to backup your registry and be safe!