I tried to install Windows 2000 SP4 and got the following error message- Service Pack 4 Setup Error: The core system file (kernel) used to start this computer is not a Microsoft Windows file. The Service Pack will not be installed. For more information, see Knowledge Base article at http://support.microsoft.com. I searched the Knowledge Base and couldn't find anything relating to this error message. Does anyone have an idea what might be going on here? I am running an OEM version of W2000 Pro/SP1. I have previously installed SPs 2 and 3 with no problems. Thanks, Bob Bulkley