you really shouldn't worry about oc'ing that video card your being helb back performance wise by that older cpu and mobo combo. Before buying that card you should ahve thought about upgrading the cpu/mobo combo as well as the pc133 ram damn to say overkill on the video card is an understatement
You should be happy with that score, since you got an extremely slow Duron and a bad mobo. Try updating the video card drivers, that got my 5200 Ultra score up by 600!!! (in 3dmark03) I also OC it, but you really shouldn't be OC the 5900 SE-YET! Maybe like in a few months or so, I would say stay away from the SE editions if you're planing to use the card MAINLY for gaming!