After I changed my old i850 mb to this msi i848 mb, my pc had this show-down-reboot problem. Basically, it can not be normally shut down, shut-down in start will lead to reboot. After checking the IRQ in system info, I found these:

IRQ 16 RADEON
IRQ 16 Intel(R) 82801EB USB Universal Host Controller - 24D2
IRQ 16 Intel(R) 82801EB USB Universal Host Controller - 24DE
IRQ 16 VIA USB Universal Host Controller
IRQ 16 VIA OHCI Compliant IEEE 1394 Host Controller
IRQ 18 Intel(R) 82801EB USB Universal Host Controller - 24D7
IRQ 18 VIA USB Enhanced Host Controller
IRQ 23 Intel(R) 82801EB USB2 Enhanced Host Controller - 24DD
IRQ 23 Realtek RTL8139/810x Family Fast Ethernet NIC
IRQ 17 VIA USB Universal Host Controller
IRQ 17 Realtek AC'97 Audio

So, when I disable both of the pci card's usb and 1394 in device manager, the pc can be shut down. This problem should not be from win2k, cause it was fine with the old i850 mb when running win2k. I think this problem looks solvable. Sometimes I need to transfer my daughter's vidoe to my pc through 1394, I will apprecaite it if you can give me some advice. Thanks