The MSI Forums is quite good really, the info is there, you just need to modify what is explained, all depends of the latest bios on the MSI website is actually the latest one? dated 30th March 2011.
Click >>
http://forum-en.msi.com/ and use the forum search function, that is how I found the info you require.
NVFlash 5.100.0.1
NVIDIA Firmware Update Utility (Version 5.100.0.1).
This DOS based software can be used to upgrade your NVIDIA video card BIOS flash ROM. You can also use it to create a backup of the BIOS on your video card.
This version adds BIOS flashing support for NVIDIA GeForce GTX 580.
Click >>
http://www.techpowerup.com/downloads/1893/NVFlash%205.100.0.1.html
Download latest Bios from MSI Website: Click >>
http://www.msi.com/product/vga/N580GTX-M2D15D5-OC.html#Download
Rename Bios file from NV801MS.KG4 to KG4.ROM
Create a USB key bootable
How to make USB key bootable:
http://www.bay-wolf.com/usbmemstick.htm
Then get attached file, and extract & copy all files nvflash.exe, CWSDPMI.EXE and KG4.rom to the USB key.
Then reboot the computer and boot from the bootable USB key,
when you see A:\ or C:\ type:
nvflash.exe -b old.rom [ENTER]
Wait process to finish, this will backup/save your current VBIOS.
Then flash the new VBIOS with:
nvflash.exe -4 -5 -6 KG4.rom [ENTER]
Wait process to finish, then reboot the machine and you're done