Assuming we are only talking about a single Virtual Disk (array) across your disks, then you can do one of two things: 1. Third-party utility.  There exist third-party utilities (such as Acronis Disk Director) that can resize partitions while keeping data intact.  These utilities are not free (rather expensive actually) ... you pay for the convenience of not having to backup/restore the data. 2. Free utilities.  Nearly any partitioning software can extend an existing partition (except Server 2000/2003 built-in DiskPart), but it can ONLY extend a partition into adjacent Unpartitioned Space, meaning that you would need to backup/delete your D: drive, extend C:, recreate D:, then restore data to it.  Server 2008 and 2008 R2 can extend a C: partition using DiskPart and/or Disk Management.  For 2003, you can use Dell's ExtPart, a Windows Vista/7/2008/2008R2, or a host of other free utilities to extend C: after deleting D:.
I have 3 160GB hard drives, I am only using 12 GB on the C Drive and 284 GB on the D drive and running low on space on the C drive. What is the best strategy for increasing space on my C drive? Thank you for your help and guidance with this questions.
Dell PowerEdge 2900 running low on space