Windows 98 hangs at starting (fails to l

I loaded a computer with Windows 98. Epox motherboard, Nvidia TN2 AGP video card. Had been working good until I installed a NIC (3com ISA Etherlink III). It won’t even allow me to Run in Safe Mode. I did the Step-by-Step mode and stops at loading the GUI (Failed to Load GUI). I already did a restore to a Last good setup but still does the same thing. Help please!!!!