JSI Tip 7027. You Experience Long Startup Times When You Start WinPE by Means of a Remote Installation Services Server?

Microsoft Knowledge Base Article 822570 contains the following Description:

Multiple client computers may take a long time to start in a Microsoft Windows Preinstallation Environment (WinPE). This long startup time may occur when clients start from a Windows 2000-based server or from a server that uses Windows Server 2003...