Mktman,  One way you can go is to use the Extpart tool found here. That program will allow you to extend the space to the C: drive. There is a catch though. With Extpart you can expand the C: drive, but only if there isn't a drive after it. So in order to expand the C: drive,  you would have to backup and delete drive D: and E:, then expand C:. Then you would recreate and restore D:and E:  Now regarding your questions, I would have to research if the update files can be moved. I know that most of the time the file that will consume the most space is the Pagefile for the OS. Which can be relocated to the E:drive.   Let me know if this helps.
This T310 system with Server 2008 Standard SP2 installed using  Dell OpenManage for a RAID array using 2 HDD's. The array is segmented into a 39mb EISA volume, a 3GB RECOVER (Drive D) volume, a 40GB (Drive C) OS volume and a 422GB (Drive E) DataPart1 Volume.  The OS drive (c:) currently has less than 1.5gb free space. I've already moved or uninstalled as much as possible, but the space seems to be used for Windows Server 2008 updates/patches. I did find about 1.2GB in the Windows/Temp folder but am uncertain if the files can be deleted without issue. Drive 'D' is the recovery disk with Drive 'E' used for program and data storage. I can't seem to find a way to expand this drive although there is sufficient space on the disk. Using the Windows Disk Management I was able to open about 20gb of free disk space that can be used to expand the OS drive - only there is no option available. Here are my questions: (1) Can I delete or move the MS Updates deployment files? If so, where are the located? (2) How can I expand the OS drive? Thanks for your assistance! Jack Leonard 
Low disk space on OS drive on PowerEdge T310 with RAID SAS 6/ir controller