NEED HELP NOW !!

I have a GEFORCE 3 ATHLON 1.4 GHZ WIN XP
512 MB RAM AND I HAVE A PROBLEM . I HAVE THE DETONATOR XP DRIVERS. Performance is not as good as it should be.(choppy video etc) and i keep getting anoying flickering lines on my screen (for example if i turn around in a first person shooter my screen will kind of flicker and slightly disjoint). HELP ME PLEASE!