and you have the new microsoft installer on your machine??
it could also be an XP thing. Probably no chance of you using on a win98 machine???
manually means you would have to flash from a boot disk or from pure DOS, which is hard from XP as far as I know.
For this way all you need is the rom file, flash utility, then run the flash utility from DOS
You should find all these programs under your MSI dir 103.
or go to nvidia bios collection
for flash utility and maybe some more info on this subject.