Optiplex 320 BIOS update - failure to flash

I need to add memory to my Optiplex 320, as it has only 256Mb. I bought the right stuff 2 512 Mb pieces, which would not be recognized.  PNY tech support said I needed to update the BIOS, currently 1.0.9, dtd 9/21/06.  I found the latest, put it on the desktop, but when I tried to run it, it says "An error was encountered trying to configure Windows to allow flashing, please reboot abd try again.  If this error re-occurs, contact tehcnical help."

I have shut down ZoneAlarm and AVG and rebooted several times, but no progress.  I looked at the DOS alternative method, but I can't locate a DOS boot disk to try that one.

I'm open to any suggestions for conquering my obstacle(s); either memory, or BIOS.

HE L P ! ! !