When attempting to install applications on Windows Server 2008, even though the user account is part of the administrator group, you will receive an error stating as follows:
"Administrator privileges are required to install a web application"
This is due to the fact that being part of the Local Administrator Group doesn't provide the same access as the Local Administrator Account (the same also applies to Windows Vista). With Windows Server 2K8, the administrator access token is split into 2 tokens when logged into the server. One of these is an administrator token and the other a standard user token. During the logon process, authorization and access control components that identify an administrator are removed, leaving a standard user token. The standard user token is used to start the desktop and, therefore, all applications that start, will be run as a standard administrator. As a result of this, the workaround is to disable the UAC (User Account Control) so that the logged in user will have the administrator token. It's interesting to note that the error that you receive isn't a UAC pop-up message, but just a general error message.
Disabling UAC
- Click Start, and then Control Panel
- Click on User Accounts
- Click on Turn User Accounts on or off
- Uncheck the User User Account Control (UAC) to help protect your computer checkbox and click OK
- Click on Restart Now
*Note, it is not recommended to leave UAC turned off due to the exposure of increased risk of malicious software attacks.
For further information regarding UAC and configuring it on Windows Server 2K8, please see Microsoft's TechNet article: http://technet.microsoft.com/en-us/library/cc709691.aspx