how to know the correct version of bios for update  

Really thankful to the link. But i have changed the mother board and processor. How did you know the manual for my system. PL.

Please also tell what is meant by these words in manual
To install an operating system that supports USB,
verify that Legacy USB support in the BIOS
Setup program is set to Enabled and follow the
operating system’s installation instructions.
I do not understand this. Think that my bios support boot from usb. I have already informed that i have 2.0 usb port support in all my usb ports.
From the reading, i could say, that my bios support legacy mode.

The details from speccy
Motherboard
Chipset Vendor Intel
Chipset Model i865P/PE/G/i848P
Chipset Revision A2
Southbridge Vendor Intel
Southbridge Model 82801EB (ICH5)
Southbridge Revision 02
System Temperature 47 °C
BIOS
Brand Intel Corp.
Version SA86510A.51T.1004.2006.0705.1741
I think that the manual is suitable for my old mothr board
Date 07/05/2006

The problem of old computer bios is that it does not contain this usb in boot priority menu.

Hi, Thanks for all the responses from all the experts. Now i know for sure, that nothing could be added to bios. Please tell what that issue in my post 12 meant

Hi, essenbe
The specification is not given by me, but actually generated. I do not remember. But i gave the speciication in my post13