I understand that it is possible to add space to the C: drive of a virtual server if it is running Windows 2008 by using diskpart after first doing so in VSPhere. Is this correct?
It depends. If the C; drive is the last partition on the disk and the additional disk space you get by expanding the virtual disk is adjacent to this partition, then you can simply use the Disk Management to resize the C: drive with Windows 2008 and newer.
yeah.. it is possible to add more space to the virtual machine with VSphere ( adding hardisk) and another option if you only have one partition like C:, you can shrink the partition using disk management after defrag the disk.
You can add disk space from vSphere GUI or command: https://www.youtube.com/watch?v=ldNuSN46tPw&feature=youtube_gdata_player