DEFRAG

Defragment hard drive.

Syntax
      DEFRAG <volume> [-a] [-f] [-v] [-?]

Options 
  volume  drive letter or mount point (d: or d:\vol\mountpoint)
  -a      Analyze only
  -f      Force defragmentation even if free space is low
  -v      Verbose output

Example:

DEFRAG c:

“How can you expect to govern a country that has two hundred and forty-six kinds of cheese?” ~ Charles de Gaulle

Related:

CleanMgr - Automated cleanup of Temp files, Internet files, downloaded files, recycle bin
DISKPART - Partition manager
pagefileconfig.vbs - PageFile Configuration