I got below solution when I tried to figured-out howto reset my forgotten DC Administrator account.
RESOLUTION:
1) Mount the Windows 2008R2 iso (i.e. SW_DVD9_SQL_Svr_Standard_Edtn_2008_R2_...9588.ISO)
2) Boot from iso.
3) Click on Repair your computer
4) In the System Recovery Options dialog box, select Use recovery tools ... option and click Next button.
5) Click the Command Prompt.
6) In the cmdline, backup the utilman.exe file from the C: or D: as shown below:
move d:\windows\system32\utilman.exe d:\windows\system32\utilman.exe.bak
6) Copy the d:\Windows\System32\cmd.exe and rename with utilman.exe as shown below:
copy d:\windows\wystem32\cmd.exe d:\windows\system32\utilman.exe
7) Restart.
8) Click the Ease of access icon.
9) In the cmdline, type the following command below to set new password of the DC Administrator as shown below:
net user administrator *
