Perhaps I'm just misssing something here.
FIC VIA-503+ motherboard, Trident video, SB 16 ISA, SupraExpress 56K modem and Windows 98SE.

Problem: When I tell the system to shut down it reboots.

Things I have tried: Shutdown supplement, reinstall of drivers for all hardware, reinstall of OS over OS, ran through Microsofts guide to shutdown problem for both 98 and 98SE, BIOS update, ran through BIOS and disabled all shadowing, tried unassigning an IRQ to VGA, disabled USB, disabled all COM ports, tried reseting BIOS to defaults, tried disablein cache on motherboard and CPU, tried different RAM, tried different CPU, replaced power supply unit (as this was bad), ran Windows Update, and I can't remember what else...

Any suggestions on what may cure this problem of rebooting when I tell it to shutdown?

Everything I have tried

------------------
BiosCentral (http://www.bioscentral.com)
BiosCentral Forums (http://www.bioscentral.com/cgi-bin/UltraBoard/UltraBoard.cgi)

I have a good idea of how frustrating it is (check topic startup-shutdown pc and you will know what agony i've been having lately) http://www.PCGuide.com/ubb/tongue.gif
I have also tried everything that's in my power.
I wonder if the problem also occurs when you use the power button to shut down (this also happens on mine).
could be some irq conflicts somewhere.
try to disable automatic irq settings in windows (and disable pnp in bios),
then let the bios determine the irq settings, mayby that helps.
I will let you know when I can finally fix my problem.
pc is still under warranty, so mayby if the computer people can't solve it, i can get a new MB or so.

see ya http://www.PCGuide.com/ubb/cool.gif