Among many other modifications, Vista came with ability to change partition size without the need of formatting. Usually you have to format the drive which results in lots of time taken by data backup, and then restoration. The other method is to install 3rd Party Software like Symantec Norton Partition Magic and Avanquest Partition Commander.
Step by Step guide:
1. Go to Start Menu, and right-click over Computer.
2. Select Manage. It will open the Computer Management window.
3. On the left panel, select Disk Management under Storage.
4. Partitions will appear on the right side, right-click the desired partition.
5. Select Extend for increasing the size and Shrink for decreasing the size.
6. A window will appear asking the new size.
7. At some cases restarting windows is needed.
Vista offers very simple resizing, but for more complex demands one should opt for Partition Magic.
Image Guide: (click on image to enlarge)
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