Can anyone help me with my internet connection?

[Jack]

I have just bought a new pc with is pretty good and the internet is slower than my other laptops. I am getting 30mb on my laptop and around 10mb on my pc.

I have done the speedtest from exactly the same location in the house with nothing else running on either machine.

I use a dongle or transmitter for the wifi as it isn't built in to the pc. would that make a difference? I tried that google public dns but that made it slower.

I am running out of ideas as most forums have the same answers i.e location in the house etc. But as the both machines have been tested from the same spot it cant be the case.

Its running on windows 7 and Virgin is the provider.

Any help would be much appreciated Jack