Ok. I have a server running Windows Small Business Server 2003. Back in the day when it was set up I naively had only a 20gb System volume, on a dynamic disk, mirrored. Unfortunately that ran out of space, so I set about extending the partition.
Windows Disk Management and Diskpart in Windows 2003 don’t allow you to extend the volume with the O/S on it. This limitation meant that I went to a tried, tested and trusted friend in GParted. Unfortunately, GParted also cannot extend volumes on dynamic disks created with the Windows LVM.
After an hour of trying to find a way to do it, I nearly ended up paying for professional tools (which do exist if you want the support and backup). I then remembered that Windows 2008 does allow you to resize the system partition.
This means that the Windows 2008 version of DiskPart can perform this function, and is included in Windows PE 3.
So, grab a copy of the Windows Automated Installation Kit from here: http://www.microsoft.com/download/en/details.aspx?id=5753 create your Windows PE 3.0 CD and boot. Instructions for creating the CD or UFD are here: http://technet.microsoft.com/en-us/library/cc749311(WS.10).aspx
Full instructions for the Windows 2008 version of DiskPart can be found here: http://technet.microsoft.com/en-us/library/cc770877(WS.10).aspx
Remember to always create a backup though.