Windows 2003 Server and Windows XP have a text based tool called diskpart.exe. It should only be used by skilled users. Also, it cannot be used to expand the system disk (aka the disk with Windows installed on it). If you are needing to expand a system drive, I recommend using PartedMagic (free) or PartitionMagic (commercial).

Diskpart.exe is a text-mode command interpreter that enables you to manage objects (disks, partitions, or volumes) by using scripts or direct input from a command prompt. Before you can use diskpart.exe commands on a disk, partition, or volume, you must first list and then select the object to give it focus. When an object has focus, any diskpart.exe commands that you type act on that object.<br /> You can only give focus to a partition on the selected disk. When a partition has focus, the related volume (if any) also has focus. When a volume has focus, the related disk and partition also have focus if the volume maps to a single specific partition. If this is not the case, then focus on the disk and partition is lost.<br /> Example to Extend a Partition:<br />

• Typediskpart to start the utility
• Typelist to get an overview over all disks and volumes
• Select the volume you want to work with i.e.select volume 2
• Now this volume is in focus you can typeexpand to use all available space

Note: This maybe a useful operation after expanding a RAID Array or adding additional capacity to a Windows 2003 Server Volume in a SAN environment.

– FredPettis - 05 May 2009