When system C: drive is running out of space, many people want to extend the system or boot partition, but few can tell from the difference between system partition and boot drive. However, the key point is how to extend the system or boot partition.
System and Boot partition
The boot partition is a disk partition that contains the boot sector and files such as NTLDR that are needed for booting Windows XP and earlier. (Windows Vista and Windows Server 2008 use a newer boot loader called bootmgr that replaces NTLDR and is configured using BCDEdit.exe)
The system partition is the disk partition that contains the Windows operating system files and its support files, but not any files responsible for booting.
The system partition can be different from the boot partition, although they are often on the same partition (drive C:). Windows setup places the initial system partition based on motherboard BIOS settings. Bitlocker requires a separate, unencrypted system partition for booting.
From the images above, both C drives are Boot partition, but one is not the system drive.
How to extend boot partition in Windows Server 2003
Unlike Windows 2008, there is no 'Extend Volume' command interates in Windows 2003 Server, diskpart command is neither able to extend the boot partition. So to extend Windows 2003 boot partition, you have to find 3rd party partition software, such as Partition Magic Server, Partition Assistant Server, etc.
2 ways to extend Server 2003 boot partition:
1. Manually shrink a data partition to get free unallocate space, and then extend the boot partition.
2. Just select which partition to take space from and then add the free space to boot partition. (The easiest way to expand boot partition.)