HELP!!I have got a problem....I am using Gigabyte GA-7VTXE motherboard, AMD Athlon 1700+,Windows XP Pro.(5.1.2600 build 2600),an old Power Supply(230W) . when I press the Shut down button in the Start Menu, WinXP shuts down but just after a second, my PC will boot again and it says "BIOS Checksum error"(the system is booting my backup BIOS, coz my Main BIOS version is F6 and my Backup BIOS is F4, the word F4 is clearly seen).....what is the problem???