Re-Partitioning on Production Server

We have a Dell Power Edge, running Raid 5 accross 4 36GB SCSI drives. It is the only Domain contoller and is running Terminal Services to push desktops to users. When the machine was installed (before my time) The C: partition was set to only 4GB(with D: having the remain 103GB). Now, with the primary partition being so small, and evry user on the network having a local profile (because of terminal Services) the drive routinely fills. So the question is: Is there a simplier way to Increase the C: partition size without a full backup/repartition/install/restore evolution? Is there an after market solution that is safe and reliable on a RAID?