Could not perform Defragmentation: Permission Needed

I have windows vista. Every time I try and defrag, windows asks for my permission. I give it. Then nothing seems to happen. As far as I can tell. It doesn't defrag. Help?

I have windows vista. Every time I try and defrag, windows asks for my permission. I give it. Then nothing seems to happen. As far as I can tell. It doesn't defrag. Help?
In Windows Vista, process of defragmentation would run silently in the background. However, this process is a bit different from that of Windows XP and under Windows Vista the graphical interface is not provided to show the defragmentation progress as in Windows XP.
If you want the graphical interface, a third party defragmentation programs shall be installed.
Here below are some defragmentation programs and choose one to use.
Have you check if you are using the computer as a Guest Account that's why you cannot start Defragment utility. That's why you will need permission to access it. Try to use the Administrator account to start the defragmentation.
And then restart your computer and then when you reached the Welcome Screen, press and hold the Ctrl+Alt keys and then press the Del key twice.
It will launch the username and password box. type Administrator on the username field and then press the Enter key. You will be logged in as the Administrator. And then try running the Defragment utility again.