If you are logged in as an administrator, you can repartition your hard disk by using the Shrink feature in Disk Management. You can shrink an existing partition or volume to create unallocated disk space, from which you can create a new partition or volume. (Note that the terms partition and volume are often used interchangeably.)
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Open Computer Management by clicking the Start button
, clicking Control Panel, clicking System and Security, clicking Administrative Tools, and then double-clicking Computer Management.? 
If you’re prompted for an administrator password or confirmation, type the password or provide confirmation. -
In the left pane, under Storage, click Disk Management.
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Right-click the volume you want to shrink, and then click Shrink Volume.
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Follow the instructions.
