It's not that Windows was installed on E: ... it is just how the partitions are enumerated.  It is normal for partitions/disks to be enumerated in alphabetical order, usually skipping a: and b: and giving the current/active/boot partition/disk drive letter C:, although utilities can assign different/specific drive letters (X: is very common to ensure it stays out of the way of existing partition enumeration, like what you are experiencing). I'm guessing that your utility is running from D:, so if your script was looking for C: as the OS partition and was finding it when installed from the Windows DVD but not with the Dell installation, then it is likely that something like this happens: OS DVD-installed:B: - System Reserved partitionC: - Windows partitionD: - bootable utility assigned (traditional/common for optical drives) Dell-installed:B: - utility partitionC: - OEM Reserved partitionD: - bootable utility assigned (traditional/common for optical drives)E: - Windows partition Just remember that Dell-installed (or installations using SBUU/SMTD/USC), create an additional partition before the Reserved partition for diagnostics, which may throw off enumeration for some applications (some backup software is commonly affected). 
I'm trying to run a dos script that references the utilman.exe file, which is apparently supposed to be on the c: drive. When I check the c: drive, the directory appears to be completely empty. Running the same script on a fresh installation from the disc supplied by Dell works, but for some reason it doesn't when I try it on the server which has the OS pre-installed. 
What is the default drive letter for Poweredge T110 running Windows 2008 
Foundation R2 ?