It’s possible to reset your Windows Sever 2008 / R2 Domain Controller administrator password using your installation CD.
1. Restart your Windows server 2008 DC with the installation CD
2. Choose your language and click next
3. Select your partition and installation version and click Next
4. Click on Comm and Line Prompt
5. Change directory to the access the system 32 directory. Then your original C:drive is changed to D: or E:depending on the number of drive and partitions you have on that system.
6. Rename the file Utilman.exe to Utilman.exe.bak using the comm and Copy Utilman.exe Utilman.exe.bak.
7. Using Command Move Cmd.exe Utilman.exe to move CMD.exe file into Utilman.exe. Press O or Y to accept after that restart your Computer normaly
8. At the user logon screen, press a combination of Windows KEY+U, then the CMD.exe will appear. Type net user “Username””new password”;
Then your system Admin Password is reset. Please don’t forget to rename back Utilman. Exe ->Cmd.exe and Utilman.exe.bak-> Utilman.exe after getting back access.