One of the cool things I really like in Windows 7 is its feature rich disk management capability, specially the capability of shrinking or extending an existing volume you have previously created and formatted. Before, in order to modifying an existing volume, I would need the help either from the command line tool diskpart or some 3rd party partition tool. Now in Windows 7, I can easily perform these operations right inside the built-in Disk Management tool.
Let’s say I have a 1-TB external hard disk that already has a 400GB partitioned in one volume.
To shrink 100GB from it to make a 300GB volume,
1. Launch the disk management tool by simply typing disk management in the search box from start menu.
2. Find the volume I want to shrink and right click on it, and pick Shrink Volume from the context menu.
3. The tool starts to scan the disk to calculate the available shrink space, which may take a little while.
Once the querying finished, it pops up a window showing the details, with the total amount of the space you can shrink in MB pre-filled in.
Type 100000 in the box, which is the amount I want to shrink from this volume.
Click Shrink button. After waiting for a little while, a shrunk volume at 300GB is ready there for me.
To extend the space in the existing volume,
1. Select the Extend volume from the context menu, which starts the Extend Volume Wizard.
2. Click Next, fill in the amount of space in MB you want to extend in the box, it shows the maximum of amount you can extend by default. In this case, type in 200000 so I can get total 500GB as the result.
3. Click Next, and Finish in the next window.
After a short period of waiting, there is an extended volume at 500GB waiting for me.
If you still prefer the Dos command version, you can use diskpart command tool to accomplish both actions. The version of diskpart in Windows 7 has been updated to have the shrink feature included.[Update on Aug 5, 2010]
As one of the comments pointed out, in order to get a more efficient shrinking result, it would be a good idea to run the Disk Defragement before performing the shrinking operation, even though the computer is smart enough knowing what to move before doing the shrink.