High Ping!!! Why?????

Hi, I'm MasterTitros From Cairo,Egypt

I have a high Ping comparing to many people in Cairo
I have:Processor : Core2duo 2.93GHz 3Mb cache 1066 MHz FBS
Video card: Niveda 7300Gs 256MB Up to 512MB
RAM: 3GB
ADSL connection with 512KB
and have Ping :280 and FPS:80-110

many people in Cairo have lower or similar Performance have a ping 50-150 and FPS 50-100

SO , Can any body tell me WHY??? & How to lower the ping??????????