Hard Drive Shrinking arranges files on an existing partition to create unallocated space that's usable for a new, separate partition on the same drive. Windows 8.1 offers a Disk Manager utility that shrinks NTFS partitions without the need for third-party software.

Limitations

Windows 8.1 can shrink only partitions that use the default NTFS file system. For FAT partitions, you'll need to use a third-party solution to shrink the drive, such as Aomei Partition Assistant or EaseUS Partition Master. Furthermore, shrinking is limited by the amount of continuous unused space -- space that can be significantly reduced by immovable system files.

Defragmentation

Defragmenting a drive optimizes used sectors, so parts of a file are closer together and more quickly accessible than in their fragmented state. A defragmented drive assists the shrinking process by reducing the amount of space necessary to maintain file integrity. Windows 8.1 automatically defrags drives on a regular schedule by default. However, you can manually defrag the drive by typing "Defragment" from the Start screen, selecting "Defragment and Optimize Your Drives," selecting a drive from the Optimize Drives window and clicking "Optimize."

Removing the Page File

The Windows paging file cannot be moved in the shrinking process, so if it's inhabiting distant sectors of your hard drive, it can severely undercut the shrinking process. If you already have several gigabytes of RAM, you can remove the paging file, reboot the system and reinstate it, so it is optimally positioned. To access these settings, type "Advanced System Settings," select "View Advanced System Settings," click "Settings" from the Performance section, choose the "Advanced" tab and then click "Change" in the Virtual Memory section. You can then uncheck "Automatically manage Paging File Size for All Drives," select a partition, choose "No Paging File" and click "Set." You'll need to reboot before the setting becomes active. Repeat the procedure and select "System Managed Size" to recreate the paging file.

Maximum Shrinkage

To access the Disk Management utility, press "Win-X" and select "Disk Management." Right-click a partition and select "Shrink Volume" to run the shrinking query. The resulting data displays the current size in megabytes, followed by the amount of shrinkable space and the amount you wish to use. The default figure in the highlighted "Enter the Amount of Space to Shrink in MB" field is the maximum size of unallocated space you can acquire. Use this number or a smaller one and click "Shrink" to shrink the volume. You can then create a new volume by right-clicking "Unallocated Space" and choosing "New Simple Volume."