Assuming you are the Administrator, if you go to Control Panel > User Accounts, you should see a link to Turn User Account Control on or off.
You should bear in mind though, that UAC is a security measure, and not only alerts you to what
you might be doing to the system at administrator level, but also what outside forces, such as a malicious program, might be attempting to do, so disabling UAC may compromise your computer's security, and you do so at your own risk!