There are many possible way to turn off or turn on User Access Control (UAC) in Windows Vista, which frequently pop up a confirmation dialog window to asking for permissions to continue a task which requires elevated administrator rights. Normally UAC cannot be enabled or disabled by using GUI-based Control Panel. For programmers or developers, it may be useful to be able to enable or disable UAC by using CLI (command line interface) commands, which can be used to automate tasks in batch script.The ability to enable or disable UAC from command prompt is actually using a trick to turn off or on UAC by using registry key. Simply open command prompt window and run the following command:

To Disable UAC
C:\Windows\System32\cmd.exe /k %windir%\System32\reg.exe ADD HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System /v EnableLUA /t REG_DWORD /d 0 /f

To Enable UAC
C:\Windows\System32\cmd.exe /k %windir%\System32\reg.exe ADD HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System /v EnableLUA /t REG_DWORD /d 1 /f
After the command, computer needs to be restarted to the change to be effective.

Ability to hibernate is enabled by default on every Windows Vista installation. If you have disable and turn off hibernation feature, accidentally delete hiberfil.sys using Hibernation File Cleaner of Disk Cleanup tool, or you just simply cannot and unable to find the Hibernate button to put the computer into hibernation state, you can re-enable or try to enable and turn on the hibernation functionality in Vista again with the following command. In Windows Vista, users no longer able to enable or disable hibernation via desktop graphical user interface.
How to Enable and Turn On Hibernation Feature in VistaClick Start button, then type Cmd in the Start Search box. In the search results list, right click on “Cmd” and click on Run as Administrator item on contextual menu. In the command prompt window, type the following command: powercfg -h on