If you want to defrag your disk but can’t, then use chkdsk first to fix common problems
Disk defragmentation is an excellent feature of Windows XP and all later versions of Windows and provides with a unique way to check disk for errors and defragment it to improve computer speed. However Windows 7 is not as famous as compared to Windows XP when it comes to issues such as battery and disk defragmentation. Windows 8 Consumer Preview also has several problems with its disk defragmentation utility since it is in infancy stages of development. Many people are complaining about the Windows Disk Defragmentation utility giving problems. Some are stating that the disk defragmentation never finishes, whereas others are complaining that it isn’t starting. Whatever the problem be, here is a good solution for you that has worked for me, and hope would do the same for you:
1. StepOpen Command Prompt using Admin mode. First search type in cmd in the metro menu search bar, right click on the icon, and select Run as Administrator from the bottom list.
2. StepWhen CMD opens up, type chkdsk/r and type in Y.
3. StepWhen you restart your system the next time, the volume shall be checked thoroughly for any errors. This is important because the disk should be error-free for defragmentation to work properly.