Saw this recommended on another question here: http://www.partition-tool.com/partition-magic/windows-server-2003-resize-partition.htm haven't tried EASEUS but it looks decent...I am more a fan of Acronis but it's pricier.  

Is this a RAID or just single disk?  If single disk you could put in another machine and use cheaper tools such as non-server Acronis or Partition Magic or whatever they call it now in a desktop machine. :)  (back up first ofc)
leew: there are nutty things people do heh, like i have a customer who runs Quickbooks POS with a server and it won't install on anything but C: according to Intuit...and it eats space like crazy.  Go figure.  Also when you install a service pack the OS tends to save a backup or whatever...and Windows does like to work on a disk that's got a lot of free space it seems.  So lately I've been making larger boot partitions.

Unfortunately the boot partition can't be done using diskpart or the GUI.

Is the disk dynamic?
If so I've had good results from Paragon Partition manager which can revert the disk to basic without losing data and then extend the disk (I've used this on all our Domain servers)

If not GParted is a good freeware tool (as mentioned by leew)

IF you're going to do things wildly against best practices, you may have little choice, but even then, there are clear and relatively EASY work-arounds, including using NTFS Junctions.

oooo sneaky leew! or even mounting a new drive at a directory on the C drive (bear in mind the folder needs to be empty first)