Unless you're using an SSD, your system will eventually suffer from performance loss when the data stored on your hard drive becomes fragmented. There's no reason to worry when this happens – it just requires a simple fix.
Hard disk drives fragment data because they are "random" by nature. Consisting of an actuator, platter, spindle, actuator arm, and read/write head (among other parts), hard drives work by storing and seeking out information on a rotating disk. When data is written (stored), it's written to the first empty portion of the drive that the write head is able to access. When a hard disk drive has written a significant amount of data, it becomes harder and harder for the drive to find all of the information or programs you want it to access in a timely manner. By defragmenting your hard drive, you can help it run more efficiently and enable faster access to data.
The best way to "defrag" your hard drive is to use the Microsoft Windows® Disk Defragmenter utility. Follow these quick steps to defrag your hard drive.
Method 2: Manually run Disk Defragmenter.
Click the Start button >> All Programs >> Accessories >> System Tools >> Disk Defragmenter. When you try to access Disk Defragmenter, you may be prompted for an administrator password or confirmation. Enter your password or provide confirmation, then click Defragment Now. Depending on the size of the drive and the level of fragmentation, it may take several minutes to several hours to complete the defrag process.
Method 2: Use Computer Management MMC.
Click Start >> Run >> then type Compmgmt.msc in the open field. Click Disk Defragmenter, then select the volume that you want to defragment. Click Defragment to begin.