Use DiskPart for 2008 and above
ExtPart.exe tool to resize partitions even the C: drive
http://support.dell.com/support/downloads/download.aspx?c=us&cs=19&l=en&s=dhs&releaseid=R64398&formatcnt=2&fileid=83929
http://taylor.freeshell.org/2009/06/dell-extpart.html.