You can find the latest BIOS for your board here: http://downloadcenter.intel.com/SearchResult.aspx?lang=eng&ProductFamily=Desktop+Boards&ProductLine=Intel%C2%AE+945+Express+Chipset+Family+Boards&ProductProduct=Intel%C2%AE+Desktop+Board+D945GNT
Aklthough unless you are wanting to update it for a specific problem that it states in teh release notes that will be fixed i wouldnt
Try the recovery method with the .bio file. You can find here the instructions: http://www.intel.com/support/motherboards/desktop/sb/CS-023360.htm
I find it to be the most relieable.
It may also be possible that you will have to do it in steps and not straight to teh last version, you will need check the release me notes to see if it says anything about it.