Computer lag or Internet lag?

I'm running a 2.8 dual core processor with nvidia 9800. When I'm in an unpopulated place I get average 50 frames per second, but when I go to the grand exchange it drops to about 15-17, do you thicken it's my computer lagging or it's just my internet being slow?

 

Check the ping of the world your playing on. I do fine on a Duo 2.0 usually with multiple accounts.

 

well does your computer start getting loud when you lag? if so, it might be your pc.
Do you use a router? that is a common cause of internet lag.
give us more details about your setup