Why Installing and uninstalling software will make your registry confusion?
When you install and uninstall software a few problems can happen. For instance, if you install photoshop on your computer, you will have to put in a code to use the program, so that the company knows that you have a real version and not some copy. After you do this, you can use the program. However, if you erase the program and reinstall it, the company that issued photoshop (adobe) will remember that it accepted your code before. So, it may not allow you to use it a second time. They do this, so that people will not share software. What you need to do is deregister the first copy and then reinstall it. In this way, there will be no problems.
Most of the software we unistall from PC will remain as it is in registry which gives problem when clogged with this invalid registry entries. Special softwares have built for resolve these kind of registry issues which is much safer than any other method.
Please use any thing registry cleaner for cleaing registry temperory files.