nope there is something way wrong, i also have a Athlon 1600+, but a soyo dragon+, 512 MB DDR, and and Xtasy GF3 Ti200. My 3DMarks2001 is 6769 so with your Ti500 you should be getting close to 8000. Also, I don't overclock anything.
OH wait, GeForce 2??? Ti500?. Ok, i guess your score is good then.