You want to move the Active Directory DIT files to a new drive to improve performance or capacity.
First, reboot into DS Restore Mode. Then, run the following commands, in which <DriveAndFolder> is the new location where you want to move the files (e.g., d:\NTDS):
> ntdsutil files "move db to <DriveAndFolder>" q q > ntdsutil files "move logs to <DriveAndFolder>" q q
You can move the Active Directory database file (ntds.dit) independently of the log files. The first command in the solution moves the database and the second moves the logs. You may also want to consider running an integrity check against the database after you've moved it to ensure everything checks out. See Recipe 16.7 for more details.
Recipe 16.2 for booting into Directory Services Restore Mode, Recipe 16.7 for checking DIT file integrity, MS KB 257420 (HOW TO: Move the Ntds.dit File or Log Files), and MS KB 315131 (HOW TO: Use Ntdsutil to Manage Active Directory Files from the Command Line in Windows 2000)