Windows Vista and Windows Server 2008 both disable administrative access when accessing via a network. So all those administrative things you're used to doing, like accessing an administrative share (\\machinename\D$) have to be thrown out when you use Vista or Server 2008.
However, you can bring it back, Windows XP / 2003 style. The key is in the registry, at KHLM\Software\Microsoft\Windows\CurrentVersion\Policies\System. Add a DWORD value named LocalAccountTokenFilterPolicy with a value of 1. Reboot.