sky broadband speed

hello I have just changed to sky broadband from virgin,I am getting approx 7mbs download on a speed check,but where ever i download anything from my download speed ends up at 8kb,Sky state that they are providing 7 mbs so the problem is my side,when using virgin I was getting up to 1.5kb from the same site,s,so could any one tell me why I am seeing a drop in the download speed from the same site,s,hope you understand what I am trying to say maybe I need to opitmise my set up but have no clue how to do so, any help gratefully received thanks for reading

peter