I know a lot of people are really annoyed by UAC or User Access Control in Windows Vista. You know, it's the the flash of the screen and a prompt for you to say it's okay to install a program or modify your system.
I actually don't mind it on my Vista system, since I only get prompted once in a while now that my system is fully configured. (I installed about twenty five programs and changed numerous settings on my last system build.) And anyone whose used MacOS or various flavors of Linux are familiar with using "elevated priviledges" to install software or make a system altering change. This usually takes place by using sudo or giving the root password. It helps protect the system from unwanted changes or inadvertent malware installs.
What I do mind is having UAC enabled on a Windows Server. It is rare indeed that I actually log onto a server unless I'm actually going to be installing software or making a configuration change that doesn't evoke the UAC. I read log files, add users and dns entries, plus much more, remotely from my client. Having to acknowledge an endless stream of prompts is ineffiecent to say the least. I know I could log onto the server as Administrator, but that's hardly best practice.
To disable UAC on Windows Server 2008 (and Vista as well), go to the Control Panel > User Accounts and click the link for Turn User Account Control on or off (and yes, if you're not logged in as Administrator a UAC prompt will appear). Uncheck the box and choose OK. A reboot is required for it to take affect.