If you open the Registry, you’ll probably find it about as cluttered as a teenager’s bedroom. That’s because Windows doesn’t efficiently clean up after itself as it goes about its daily business. It constantly creates new entries, but it seldom–if ever–removes them after they’re no longer needed.
Compounding that problem are applications that are too inept to uninstall all of the Registry entries that they create. Far too often program upgrades and installers leave unneeded pointers in the Registry. So the Registry becomes weighted down with unnecessary entries, slowing down your system.