Your PC is not necessarily slow BUT the SDRAM will be killing a lot of the performance of the P4

- and from what I have seen NBA Live 2003 seems to be quite memory hungry. The video card is quite good, however...
other EA games like madden 2k3, fifa 2k3 and nhl 2k3 run smooth at highest details but nba live 2003 not at all!
I find the other EA games seem to run smoother on my computer in comparison to Live, pehaps they are coded better graphically? A lot of people seem to be struggling to get good performance...
All I can suggest is make sure all your drivers are up to date (video card, chipset etc.) if they aren't already, instead of cranking down the details perhaps you can crank the resolution down a notch or two (usually brings about instanct frame rate increases)
Sorry, but I don't have any other ideas

but the best of luck, anyway