Windows Server 2008\Can’t perform a “RunAs” during an installation
So far, my experiences with Windows Server 2008 has been less than stellar, from a application server perspective. One bad caveat, the Windows 2008 Server RTM code does not allow you to perform a RunAs on any account other than the “administrator”. This is especially bothersome when you are trying to run or install an application using a different credential. (i.e., Exchange 2007)
Microsoft’s newly acquired Sysinternals has a new utility that restores this functionality.
From the command-line perform a "shellrunas /reg"
So far it has worked great, however, one thing to note, is you must run this command on every user needing the functionality. It appears to install on a per-user basis.