The registry on your computer is essentially like a road map, telling your computer where things are and when to turn them on. On occasion, if you run into trouble, you will be required to enter into your registry to fix the problem.
However, the registry is extremely important and only users who know what they are doing should make changes; that or make sure you have the guidance of someone who knows what they are doing. While it is difficult to really mess up a computer, making bad changes in the registry is a good way to cause a disaster.
The problem is, every time you add or delete software from your computer your registry gets a little bit gummed up, interfering with the ability of your computer to follow the road map quickly. This and other entries can cause your computer to slow down. The way I personally deal with this issue is something called a registry cleaner.
I should tell you that registry cleaners are a bit controversial; not because they cause harm to your computer, but because there is a dispute as to whether they work. I feel they work and I consistently use one on my computer.
The cleaner I use is called cCleaner and it may be downloaded for free here.
Another way to keep your computer running quickly is to run the Microsoft Defrag tool. Over time computer hard drives become fragmented because of the way in which files are written. The fragmentation of the drive causes the computer to slow down. The defrag tool is under Accessories on your computer.
It shows both cCleaner and the defrag tool. In addition to discussing the registry aspect of cCleaner I also show other abilities of cCleaner including removing extraneous information in your Web Browser(s), removing software, etc. (My reference to snow is because I recorded the video during a major snow storm.)
To enlarge the video click on the full screen window on the bottom right of the video.