Registries get bigger and cause boot-ups to take a bit longer over time.  http://www.pcmatic.com will tell you what is worth fixing or not on your system.  If you see names of apps that you are familiar with listed as problems, you have nothing to worry about and so you can just uninstall the diagnostic program after it reports what it finds.  Don't spend the money to clean your registry just to save a few seconds when booting up your PC.

Incredimail is fun to remove if you like manual registry editing.  There are others like Gater Games and Wild Tangent.

www.youtube.com/user/ShawnDriscollCG