Quoted from http://windows7.iyogi.net/tips/windows-7-tips-user-account-control-uac:
Make UAC Less Annoying On Windows 7Problem: How to disable UAC?Solution: User Account Control prevents your computer against hackers and defend it against malicious software. UAC asks the user for the permission, if any program wants to make any changes to your computer. UAC is more flexible in Windows 7 than in Windows Vista.No doubt UAC is an essential tool for us, but still we can disable User Account Control to make it less irritating.
Instructions to disable UAC on Windows 7:* Just type UAC into the start menu or Control Panel search box.
* You can simply drag the slider up or down, depending on how often you want to be alerted.
* If you drag it completely down to the bottom, you have disabled it entirely.Note: Disabling UAC will lead to a less secure system, so be careful.