Tune up your PC with Optimize Disk

Optimization rearranges scattered file fragments into adjacent or contiguous clusters. This allows files to be read into memory faster. Optimization also consolidates free space to avoid fragmenting newly added files. It adds extra space after major data structures so that they can grow without immediately becoming fragmented again.

Your computer's hard disk stores all of your files, applications, and the Windows operating system. Over time, the bits of information that make up your files gradually spread over the disk. This process is known as fragmentation. The more you use your computer, the more fragmented your disks become.
The operating system tries to store file data in contiguous sectors on the disk, so that the drive heads can move sequentially, reading each sector in turn. When a file is deleted, the operating system tries to reclaim that deleted space. If a new file being written is bigger than the contiguous space available, the operating system will have to fragment the file. Reading and writing now involves the drive heads having to move across the disk to find all the fragments of the file, thus, slowing down the process. Over time, more files are added and deleted, which increases this fragmentation and lowers the performance of the computer. Defragmentation is the rearranging of these sectors so that file data is stored contiguously.