I understand when you try to install AutoCAD Civil 3D 2010, you receive an error messages, "Error 1327. Invalid C:\", "Fatal error during installation. #7560: failed to run AdskExecuteSequence", and "Failed to initialise AutoCAD Civil 3D 2010", and are unable to get beyond the initial selection of products to install . As well, when you installed windows, the drive assignment became 'H' instead of 'C'.
The following link is support information to change the drive letter assignment for Windows XP. If you're on a different Operating System (O/S), you may want to perform a search on Microsoft's site to find that particular information. Microsoft Support - How to change the driver letter assignment in Windows XP
One test to try is to create a folder in the 'H' drive and copy the C3D files from the DVD to this folder; proceed to install from the folder.
Try changing the drive assignment first before installing from the DVD, if that does not work try the other test to copy the data from the DVD to the 'H' drive.
Please let me know if this information helps resolve the installation issue.
Autodesk Product Support