If the DHCP server database becomes corrupted or is lost, recovery is possible by replacing the server database file (Dhcp.mdb), located in the %SystemRoot%\System32\Dhcp folder, with a backup copy of the same file.
If DHCP Manager was used previously to perform a backup, you can obtain the backup copy of the server database file located in the %SystemRoot%\System32\Dhcp\Backup folder. You can also restore the Dhcp.mdb file from a tape backup or other backup media.
To perform these procedures, you must be a member of the Administrators group, or you must have been delegated the appropriate authority.
To restore a backup copy of the DHCP database:
Click Start, click All Programs, click Accessories, right-click Command Prompt, and then click Run as Administrator.
Type net stop dhcpserver, and then press ENTER.
Type md c:\olddhcp, and then press ENTER.
Type move %SystemRoot%\system32\DHCP\*.* c:\olddhcp, and then press ENTER.
Type del %SystemRoot%\system32\DHCP\Dhcp.md, and then press ENTER.
Type copy %SystemRoot%\system32\dhcp\backup\jet\new\dhcp.mdb %SystemRoot%\system32\dhcp\dhcp.mdb, and then press ENTER.
Type net start dhcpserver, and then press ENTER.