Power options in windows vista not working

[Imtiyaz]

Hello there,

I have desktop running windows vista. When i change something in power options, it won't work at all. Can anyone help me with this?

thank you in advance.

Check if you are logged in with administrator account. you must be logged on as an administrator to change any of your computer's power settings. Windows hides power management settings that your computer doesn't support.
If the computer is actively sharing files or media then it will not go to sleep. Check your multimedia settings in advanced settings.

[SalVatore]

In order to allow your computer to automatically go to sleep if it is left idle, you can explicitly allow it to go to sleep when sharing media. You should note though that if you are trying to access media on this system when it goes to sleep, you will no longer be able to. If you are happy to do this, then you should do the following:

• Open Power Options in Control Panel
• Click on Change plan settings below the power plan that you use
• Click on Change advanced power settings
• Click the + next to Multimedia settings
• Click the + next to When sharing media
• Change the setting to Allow the computer to sleep
• Click OK then Save changes

[jesse]

Go to power option and set all to default. Then restart your system. Just give a try.

Check this for some more information:
http://support.microsoft.com/kb/927393
http://support.microsoft.com/kb/928897