The only way to fix that is by reinstalling Windows.  If you delete and
create partitions while you are installing Windows you should reboot and
restart the setup after you create new partitions, this avoids drive
letter assignments mix ups like the one you have experienced.  If you
have more than one disk installed the active partition on the first disk
will be assigned the "C" drive letter.  If you have multiple disks
installed in the computer you can either move them to different
positions on the disk controllers, temporarily disconnect them or turn
off the unused disks while you install Windows, those other disks can be
brought on line after Windows is installed.  If you have disks on
different controllers keep in mind that the disks on the IDE controller
are almost always the first ones to be enumerated.  You can read here
for more information:

How Windows 2000 Assigns, Reserves, and Stores Drive Letters
http://support.microsoft.com/kb/234048

John

Have the same problem. Since I did not want to reinstall Windows, I did a
"subst c: f:" command in auto-start.
This helps those incorrectly written software with getting to C:
Anyway, you will experience some problems for example with external USB
drives - these will most probably get enumarated as first available letter
which is still C:
You will need to manually reassign drive letter for such external drive, but
besides this everything is working fine for me.