I can't seem to down load a driver every site I go on wants money I have standard graphics adapter I can adjust screen help am two seconds away from busting this !
Something is wrong with that link I posted above. I don't know why it doesn't go to the page I got it from. It's supposed to go direct to the GX620 driver page.
If that still takes you to the wrong page, just do a Google search for "dell optiplex gx620 drivers" and click on the "optiplex gx620 driver - Product Support | Dell US" hit when it comes up.