Slow Airport Extreme (Old Model)

I bought the old model airpot extreme off ebay dirt cheap. At first it was flawless, worked fine with my student halls internet and had no bugs. Then one day it slowed down to literally dialup speed. So i reset it and it worked for a few hours and then slowed down again. It keeps doing this and most of the time its just slow all the time. Right now iv moved back to using ethernet cables which defeats the object really lol.

Any help will be much appreciated!
Sam