display problems after installing directx9.0b

i downloaded directx9.0b and another nvidia display
driver from windowsupdate.com(unfortunately the exact
name of the software escapes me)and since installing
these updates, i cannot view my perferred screen
resoultioun in full screen, nor can i play my games in
full screen. the only resolution that i can view in full
screen is 1400x1050, which woulb be ok, but all games
that i play are tiny, i cannot play them in full screen.
my graphics card is an nvidia geforce2 go 16mb. thank you