I have installed Windows Vista on a computer using ImageX from WinPE. I followed the instructions here for partitioning the hard drive, creating a 300 MB system partition and using the rest of the drive for a Windows partition. The install has worked perfectly apart from the fact that the system partition has been assigned the drive letter C: and the Windows has been assigned the drive letter D:. I would like the system drive to have no letter and the Windows partition to have the drive letter C:. I think I have managed to figure out why it is doing this. See my answer below. Can anyone confirm this?