I have a Dell Optiplex GX1, 500 MHz P3, 256MB RAM.  Win XP loaded as an upgrade from Win 98.  It insists on trying to boot from the LAN, loads 3 Com PXE LANworks whether an ethernet cable is connected or not.  I have tried all the boot sequence options - CDROM, floppy, hard drive only, boot list -  and they make no difference. The LAN connection is on board so I can't remove it. Wake on LAN is disabled in the setup menu.  I don't see any other options there that could help.
How can I get past the LAN boot so XP will load?

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