There are ways to extend partition in Server 2003 basic disk, the best partition software should be fast solve problems like low disk space and running out of space problems, not meet any not enough space warning when upgrade to Server 2008 or 2012.
What is Basic Disk?
Basic disks are the storage types most often used with Windows. The term basic disk refers to a disk that contains partitions, such as primary partitions and logical drives, and these in turn are usually formatted with a file system to become a volume for file storage.
—Microsoft, read more on disk type
Partition Extender is able to extend partition in Server 2003 Vmware, you may found that Extender runs fast in Server 2003 Vmware just like it runs in local pc, Since Extender will not any data in partition or in Vmware disk partitions,
Vmware is often used to test utilities that might be help in some way, before running them in local pc, they would be tested in Vmware to check if they are green or not, Virus free or not, work well or not, anything like that. So partition size in Vmware partitions is often running in low disk space.
Active Partition is often sat at the beginning of partitioning, because Server System can only be installed in active partition, if you haven't distribute enough disk space to active partition, Server performance will be infected even after you successes installed system.
Partition Extender can extend active partition in Windows Server 2003 without data loos and reboot, here are the steps to extend active partition in Server 2003, steps are alike even it links to guide steps of Windows 10
Boot partition, active partition, primary partition sometimes mean C Drive, C partition, System partition. Extend boot partition in server system is often required in daily use, data can be enlarged overnight when Server system running without stop in big companies.