I have a Thunderbird 1.4GHz with a 9600 Pro and its pretty playable on Q3A. I get 3000+ 3DMark 03 scores too. I would say your Duron 750, despite being only half as fast, should be able to handle Q3A 640x480 pretty easily. Heck, my old C300@450 with a Voodoo3 3000 could handle Q3A at 800x600 at 60+FPS avg.