User Account Control (UAC) is a security component in Windows Vista. UAC enables Windows to distinguish between administrator users and non-administrators or standard users. It aims to improve the security of Microsoft Windows by limiting application software to standard user privileges until an administrator authorizes an increase or elevation. In this way, only applications trusted by the user may receive administrative privileges, and malware should be kept from compromising the operating system. You can find more about UAC on Wikipedia.
You may find this new security component little annoying and you may want to disable it. I personally encourage you not to but if you are really sure on what you want you should …
1. Click on Start -> Contol Panel ->User Accounts
2. Click on Turn User Account Control on or off
A UAC window will pop-up, click Continue.
3. Clear the selected radio button Use User Account Control (UAC) to help protect your computer
4. Click on OK than Restart Now