System partition is very likely running out of space, because many types of junk files are generated in it continuously. You'd better try to solve this problem before C drive becomes full, otherwise you'll encounter much issue such as server stuck, reboot unexpectedly or even crash. It costs such a long time if you recreate partitions and restore everything from backup.
It is much faster and easier if you expand system partition, but before starting, you'd better make a backup and run safe partition software, because there's potential system damage and data loss risk while resizing disk partitions. Better than other software, NIUBI Partition Editor has advanced technologies to protect system and data:
In most cases, there's at least 1 data partition on the same disk. You can shrink this data partition with NIUBI, then part of unused space will be converted to Unallocated. System partition will be extended by adding this space. In this way, Operating System, programs and associated settings, as well as anything else keep the same with before (except partition size). No other operations are needed even if you use any types of hardware RAID arrays.
Follow the steps to extend system/os partition on Windows Server 2003:
What to do if there's no data partition or not enough free space on the system disk? Some people ask whether it's possible to extend system volume by taking free space from a partition on another disk. The answer is no, because the size of a physical hard disk is fixed, a 250GB disk can't be decreased to 200GB or increased to 300GB.
When the whole system disk is full, you can copy it to a larger disk with NIUBI Partition Editor, additional disk space can be added to system drive.
Follow the steps to expand system volume on Windows Server 2003 with another disk:
It requires server rebooting to execute.
If you run this server as a virtual machine in VMware or Hyper-V, you can extend system drive for Server 2003 without copying to other disk.
If there's available free space on the same disk, there's no difference, simply follow the steps in the first video above. If there's no available free space, you can expand system disk directly, follow the steps:
After expanding disk, additional space is shown as Unallocated on the end, then you can move and add Unallocated space to system C drive (and other volumes). Besides shrinking and extending partition, NIUBI Partition Editor helps do many other disk partition operations.