Your hard disk is the storage device that holds the entire Windows operating system and all of your important files and data. Through normal use of your computer, your hard disk will become cluttered with hundreds or even thousands of Junk Files. These junk files are created by Windows and other programs that writes temporary files, during installation and when running, to your hard disk which they need to do in order to work.
The problem is often that these junk files are not removed from your hard disk, even after they are no longer needed, and waste important disk space for your computer to run optimally. A hard drive has a limited amount of space. If you run out of hard drive space, your computer may lock up, crash, or even fail to start-up. The more files you have on your hard drive, the more time it can take to access files while using the computer, the more data you have on your hard drive, the performance is much slower. Removing the garbage files from your system can regain megabytes or even gigabytes of valuable disk space on your hard drive. This will give you more hard drive space for new programs as well as data files like pictures, movies or other important files and helps avoid possible computer issues caused by low disk space.
There is a software called CCleaner that can remove your unwanted junks in few clicks and monitor junk file size in the background. It really does a good job. You Can download CCleaner form here.
CCleaner can remove and clean junk from: