User Account Control (UAC) is the biggest security improvement to Windows Vista, and you’ll hate it.
You see, sometimes, bad software (known as spyware, viruses, or malware) can abuse your user account to change settings on your computer. It happens to everyone, including me (several times). One of the most effective ways to stop this software is to strip away your user accounts’ rights to make changes or install software. That’s what UAC does–it gives you an account that can’t install software or make important changes.
Of course, sometimes you’ll want to make a change. That’s when UAC will prompt you for confirmation. If you’re doing something like installing software or changing your computer’s clock, go ahead and click Continue or type the password for an administrative user account. If you’re just browsing the Web or reading e-mail, click Cancel, because some bad software might have caused the prompt to appear. If you’re just sick of UAC and you have antispyware and antivirus software installed, you can follow these instructions to disable UAC.